Hydro One Dg Technical Interconnection Requirements Distribution Interconnections

DISTRIBUTED GENERATION
TECHNICAL INTERCONNECTION
REQUIREMENTS
INTERCONNECTIONS AT VOLTAGES 50KV AND
BELOW

Proposal for Stakeholder Consultation

© COPYRIGHT 2009 HYDRO ONE NETWORKS LTD. ALL RIGHTS RESERVED

Rev 0
February 2009

DISTRIBUTED GENERATION TECHNICAL INTERCONNECTION REQUIREMENTS
Hydro One Networks Inc. INTERCONNECTIONS AT VOLTAGES 50KV AND BELOW

LIMITATION OF LIABILITY AND DISCLAIMER

Hydro One Networks Inc.’s (“Hydro One”) “Distributed Generation Technical Interconnection
Requirements: Interconnections at Voltages 50kV and Below” (the “DG Requirements”) identifies
minimum requirements for generation projects connecting to Hydro One’s distribution system.
Additional requirements may need to be met by the owner of the generation project to ensure that
the final connection design meets all local and national standards and codes and is safe for the
application intended. The DG Requirements are based on a number of assumptions, only some of
which have been identified. Changing system conditions, standards and equipment may make
those assumptions invalid. Use of this document and the information it contains is at the user’s
sole risk. Hydro One, nor any person employed on its behalf, makes no warranties or
representations of any kind with respect to the DG Requirements, including, without limitation, its
quality, accuracy, completeness or fitness for any particular purpose, and Hydro One will not be
liable for any loss or damage arising from the use of this document, any conclusions a user derives
from the information in this document or any reliance by the user on the information it contains.
Hydro One reserves the right to amend any of the requirements at any time. Any person wishing to
make a decision based on the content of this document should consult with Hydro One prior to
making any such decision.

STAKEHOLDER CONSULTATION CONTACT

Please forward questions/comments regarding this Document to the following email address:

EMAIL: DGConnectionReq@hydroone.com

Hydro One has released this document for public stakeholder consultation. The stakeholder consultation
process along with an electronic version of this document is available at www.hydroone.com/DG

REVISION HISTORY

DATE VERSION COMMENTS
Proposal – Rev 0
February 2009 New Report

Rev 0
February 2009


Rev 0
February 2009


TABLE OF CONTENTS
TABLE OF CONTENTS ..................................................................................................................................... 1
LIST OF FIGURES ............................................................................................................................................. 5
LIST OF TABLES ............................................................................................................................................... 6
1 INTRODUCTION .................................................................................................................................. 7
1.1 SCOPE ................................................................................................................................................. 8
1.2 DOCUMENT REPRODUCTION .............................................................................................................. 9
1.3 TERMS AND DEFINITIONS ................................................................................................................. 10
2 HYDRO ONE SYSTEM CHARACTERISTICS ................................................................................. 16
2.1 GENERAL CHARACTERISTICS ........................................................................................................... 16
2.2 SYSTEM FREQUENCY ........................................................................................................................ 16
2.3 VOLTAGE ......................................................................................................................................... 16
2.4 VOLTAGE REGULATION ................................................................................................................... 17
2.5 VOLTAGE AND CURRENT UNBALANCE ............................................................................................. 18
2.6 POWER QUALITY .............................................................................................................................. 18
2.7 FAULT LEVELS ................................................................................................................................. 18
2.8 SYSTEM GROUNDING ........................................................................................................................ 19
2.9 HYDRO ONE NETWORKS INC. DISTRIBUTION SYSTEM FEEDER PROTECTION .................................. 19
2.10 AUTOMATIC RECLOSING (FAULT CLEARING) .................................................................................. 20
2.11 PHASING ........................................................................................................................................... 21
2.12 MULTIPLE SOURCE (NETWORKED) SYSTEM ..................................................................................... 21
2.13 FREQUENCY OF INTERRUPTIONS ...................................................................................................... 21
2.14 ABNORMAL CONDITIONS .................................................................................................................. 22
3 DG TECHNICAL INTERCONNECTION REQUIREMENTS .......................................................... 23
3.1 INTERCONNECTION TECHNICAL REQUIREMENTS............................................................................. 24
3.1.1 Safety ......................................................................................................................................... 24
3.1.2 Adverse Effects to HONI Customers ....................................................................................... 24
3.1.3 Point of Common Coupling ...................................................................................................... 24
3.1.4 Point of Disconnection .............................................................................................................. 26
3.1.5 Voltage ....................................................................................................................................... 27
3.1.6 Voltage and Current Unbalance ............................................................................................... 28
3.1.7 Frequency .................................................................................................................................. 29
3.1.8 Power Factor ............................................................................................................................. 29
3.1.9 Capacity Limitations on Generator Interconnections .............................................................. 30
3.1.9.1 Three Phase Generator Interconnections ........................................................................................... 30
3.1.9.2 Single Phase Generator Interconnections .......................................................................................... 30
3.1.10 Phasing Requirements ............................................................................................................. 31
3.1.11 Interconnection Transformer Configuration............................................................................. 31
3.1.11.1 DG Interconnection to 4-Wire Distribution System ........................................................................... 32
3.1.11.2 DG Interconnection to 3-Wire Distribution System ........................................................................... 41
3.1.12 High Voltage Interrupting Device (HVI) ................................................................................... 44
3.1.12.1 Requirement for Interconnection to 4-Wire Distribution System ...................................................... 45
3.1.12.2 Requirement for Interconnection to 3-Wire Distribution System ...................................................... 45
3.1.12.3 Interrupting Time Requirement .......................................................................................................... 45

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3.1.13 Station Service for Critical Loads ............................................................................................. 45
3.1.14 Grounding .................................................................................................................................. 46
3.1.15 Fault Levels ............................................................................................................................... 48
3.1.16 Resonance Analysis ................................................................................................................. 48
3.1.17 Self-Excitation Analysis ............................................................................................................ 49
3.1.18 Islanding..................................................................................................................................... 49
3.1.19 Synchronization ......................................................................................................................... 49
3.1.20 Insulation Coordination ............................................................................................................. 51
3.1.21 Equipment Rating and Requirements ...................................................................................... 51
3.1.22 Operating Requirements .......................................................................................................... 52
3.1.23 Metering ..................................................................................................................................... 53
3.1.24 DG Facility Acceptance ............................................................................................................ 53
3.2 PROTECTION REQUIREMENTS .......................................................................................................... 54
3.2.1 General Requirements.............................................................................................................. 54
3.2.2 Hydro One Networks Inc. Distribution System Feeder Protection......................................... 55
3.2.3 Sensitivity and Coordination ..................................................................................................... 55
3.2.4 Protection Operating Times...................................................................................................... 55
3.2.4.1 Interrupting Time for Device Disconnecting Generation ..................................................................... 56
3.2.5 Interrupting Device Rating ........................................................................................................ 56
3.2.6 High Voltage Interrupter (HVI) .................................................................................................. 56
3.2.7 Breaker Fail (BF) ....................................................................................................................... 58
3.2.7.1 BF Protection for HVI............................................................................................................................ 58
3.2.7.2 BF Protection for LVI ............................................................................................................................ 59
3.2.8 Single Phase Generators ......................................................................................................... 59
3.2.9 Three Phase Generators .......................................................................................................... 61
Delta:Wye DGIT Connecting to 3-Wire – Preferred ............................................................................ 63
3.2.9.1
3.2.9.2 Wye-Gnd:Delta DGIT Connecting to 3-Wire - Alternate ..................................................................... 64
3.2.9.3 Wye-Gnd:Delta:Wye-Gnd Connecting to 3-Wire - Alternate .............................................................. 65
3.2.9.4 Wye-Gnd:Delta DGIT Connecting to 4-Wire - Preferred .................................................................... 66
3.2.9.5 Wye-Gnd:Delta:Wye-Gnd Connecting to 4-Wire - Alternate .............................................................. 67
3.2.9.6 Delta:Wye DGIT Connecting to 4-Wire - Alternate ............................................................................. 68
3.2.10 Phase and Ground Fault Protection Requirement .................................................................. 69
3.2.11 Unbalance Protection................................................................................................................ 70
3.2.12 Feeder Relay Directioning ........................................................................................................ 71
3.2.13 Over Frequency/Under Frequency Protection ........................................................................ 71
3.2.14 Overvoltage/Undervoltage Protection...................................................................................... 73
3.2.15 Anti-Islanding Protection ........................................................................................................... 74
3.2.16 Requirement for Transfer Trip .................................................................................................. 75
3.2.16.1 Possible Exemption for DGs Smaller than 500kW ........................................................................... 76
3.2.17 DGEO (Distributed Generator End Open) ............................................................................... 76
3.2.18 Unintentional Energization........................................................................................................ 76
Connection to Hydro One Network’s System.......................................................................... 77
3.2.19
3.2.20 Disconnection of DG facilities .................................................................................................. 77
3.2.20.1 Disconnecting DG Generation ........................................................................................................... 78
3.2.20.2 Disconnecting DG HV Ground Sources ............................................................................................ 78
3.2.21 Reconnection of DG Facility ..................................................................................................... 78
3.2.21.1 Reconnection of Hydro One Source (for a transient fault) ............................................................... 78
3.2.21.2 DG Facility Reconnection................................................................................................................... 79
3.2.21.3 Lock-Out of Hydro One Source (For a Permanent Fault) ................................................................ 81
3.2.21.4 Restoration Following a Sustained Outage or Shutdown................................................................. 82
3.2.22 LSBS (Low Set Block Signal) ................................................................................................... 82
3.2.23 Auto-Resynchronization/Reconnection ................................................................................... 82
3.2.24 Synchronization Protection ....................................................................................................... 83
3.2.25 Telemetry and Targeting .......................................................................................................... 83

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3.2.26 Transformer Protection ............................................................................................................. 84
3.2.27 Protection from Electromagnetic Interference (EMI) .............................................................. 84
3.2.28 Surge Withstand Performance ................................................................................................. 84
3.2.29 Special Interconnection Protection .......................................................................................... 84
3.2.30 Batteries/DC Supply.................................................................................................................. 85
3.2.31 Protection Scheme Failure ....................................................................................................... 86
3.2.32 Teleprotection Scheme Failure ................................................................................................ 86
3.2.32.1 Transfer Trip Channel Failure ............................................................................................................ 86
3.2.32.2 DGEO Channel Failure ...................................................................................................................... 87
3.2.33 Generators Paralleling for 6 Cycles or Less (Closed Transition Switching) ......................... 87
3.2.34 Instrument Transformers for use in Protection Systems ........................................................ 87
3.2.35 Provision for Future Changes .................................................................................................. 87
3.2.36 Interconnection Protection Acceptance ................................................................................... 88
3.2.37 Protection Summary ................................................................................................................. 89
3.3 CONTROL AND TELECOMMUNICATIONS REQUIREMENTS ................................................................. 90
3.3.1 General ...................................................................................................................................... 90
3.3.2 Control Facilities ........................................................................................................................ 91
3.3.3 Telecommunication Facilities ................................................................................................... 91
3.3.3.1 Reliability Requirements....................................................................................................................... 92
3.3.4 Operating Data, Telemetry and Monitoring ............................................................................. 93
3.3.4.1 Class 1 Generators ............................................................................................................................... 93
3.3.4.4 Class 4 Generators............................................................................................................................... 95
3.3.4.5 Telemetry Reporting Rates .................................................................................................................. 95
3.3.5 Monitoring Reporting................................................................................................................. 96
3.4 PERFORMANCE REQUIREMENTS ....................................................................................................... 96
3.4.1 Power Quality ............................................................................................................................ 96
3.4.1.1 Voltage Fluctuations (Flicker) .............................................................................................................. 97
3.4.1.2 Voltage and Current Harmonics........................................................................................................... 97
3.4.1.3 Voltage and Current Unbalance........................................................................................................... 98
3.4.1.4 Limitation of DC Injection ..................................................................................................................... 98
3.4.2 Disturbances.............................................................................................................................. 99
3.4.3 Generator................................................................................................................................... 99
3.4.3.1 Reactive Power Requirements ............................................................................................................ 99
3.4.3.2 Speed Governors................................................................................................................................ 100
3.4.3.3 Excitation Equipment .......................................................................................................................... 101
4 METERING REQUIREMENTS ........................................................................................................103
5 CONNECTION PROCESS REQUIREMENTS .................................................................................103
5.1 IMPLEMENTATION ...........................................................................................................................103
5.2 CONNECTION AGREEMENT..............................................................................................................104
6 COMMISSIONING AND VERIFICATION REQUIREMENTS ......................................................105
6.1 HYDRO ONE NETWORKS INC. COVER PROCESS ...........................................................................105
6.2 HYDRO ONE REQUIREMENTS FOR COMMISSIONING AND VERIFICATION ........................................105
7 MAINTENANCE REQUIREMENTS ................................................................................................107
7.1 PROTECTION AND CONTROL SYSTEMS EQUIPMENTS ......................................................................107
8 REPORTING REQUIREMENTS FOR DGS .....................................................................................108
9 REFERENCES ....................................................................................................................................110

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A APPENDIX A - DEVICE NUMBER DESCRIPTION .......................................................................113
APPENDIX B – NEUTRAL REACTOR AND GROUNDING TRANSFORMER IMPEDANCE
B
CALCULATIONS FOR INVERTER BASED DG FACILITIES ......................................................114
APPENDIX C – TIMING DIAGRAMS ..............................................................................................115
C
APPENDIX D – ANTI-ISLANDING PROTECTION ........................................................................119
D
APPENDIX E – DGEO & LSBS DESIGN CONSIDERATIONS ......................................................134
E
APPENDIX F – EXAMPLE OF A SEQUENCE OF EVENTS DURING FAULT CONDITIONS...135
F
APPENDIX G – CONFIRMATION OF VERIFICATION EVIDENCE REPORT ..........................137
G
APPENDIX H – DISTRIBUTION POLICY – METERING FOR DG - NOP 041 ...........................145
H

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List of Figures

FIGURE 1: SIMPLIFIED SLD – SHOWS CLEARLY IDENTIFIED PCC .......................................................................... 25
FIGURE 2: PREFERRED DGIT CONFIGURATION FOR 4-WIRE DISTRIBUTION SYSTEMS ............................................. 34
FIGURE 3: ALTERNATE DGIT CONFIGURATION FOR 4-WIRE DISTRIBUTION SYSTEMS ............................................ 36
FIGURE 4: ALTERNATE #2 DGIT CONFIGURATION................................................................................................. 39
FIGURE 5: ALTERNATE DGIT CONFIGURATION FOR FACILITIES < 1 MVA .............................................................. 40
FIGURE 6: PREFERRED DGIT CONFIGURATION FOR 3-WIRE DISTRIBUTION SYSTEM ............................................... 42
FIGURE 7: ALTERNATE DGIT CONFIGURATION FOR 3-WIRE DISTRIBUTION SYSTEM .............................................. 43
FIGURE 8: ALTERNATE DGIT CONFIGURATION FOR 3-WIRE DISTRIBUTION SYSTEM .............................................. 44
FIGURE 9: EXAMPLE PROTECTION FOR A SINGLE PHASE GENERATOR ................................................................... 60
FIGURE 10: PREFERRED CONNECTION FOR 3-WIRE DISTRIBUTION SYSTEM ............................................................ 63
FIGURE 11: ALTERNATE CONNECTION FOR 3-WIRE DISTRIBUTION SYSTEM ........................................................... 64
FIGURE 13: PREFERRED CONNECTION FOR 4-WIRE DISTRIBUTION SYSTEM ............................................................ 66
FIGURE 16: NPCC DIRECTORY D2 REQUIREMENT ............................................................................................... 72
FIGURE 17: NO TRANSFER TRIP WITH 500MS RECLOSURE UPSTREAM ..................................................................115
FIGURE 18: NO TRANSFER TRIP WITH 1S RECLOSURE UPSTREAM ........................................................................116
FIGURE 19: TRANSFER TRIP WITH 500MS RECLOSURE UPSTREAM ........................................................................117
FIGURE 20: TRANSFER TRIP WITH 1S RECLOSURE UPSTREAM ..............................................................................118
FIGURE 21: TYPICAL DISTRIBUTION SYSTEM WITH DG INTERCONNECTIONS .........................................................129
FIGURE 22: DGEO & LSBS DESIGN CONSIDERATION .........................................................................................134
FIGURE 23: SEQUENCE AND TIMING DIAGRAM FOR TRANSIENT FAULTS ..............................................................135
FIGURE 24: SEQUENCE AND TIMING DIAGRAM FOR PERMANENT FAULT ...............................................................136

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List of Tables

TABLE 1: VOLTAGE LIMITS 0 TO 50,000V ON DISTRIBUTION SYSTEM ................................................................... 17
TABLE 2: OPERATING FREQUENCY RANGE ........................................................................................................... 29
TABLE 3: RESYNCHRONIZATION REQUIREMENTS .................................................................................................. 50
TABLE 4: ARRESTER RATINGS .............................................................................................................................. 51
TABLE 5: TYPICAL PROTECTIONS REQUIRED FOR SINGLE PHASE DG FACILITIES ................................................... 60
TABLE 6: TYPICAL PROTECTIONS FOR THREE PHASE DGS ..................................................................................... 62
TABLE 7: OVER/UNDER FREQUENCY PROTECTION SET POINTS AND CLEARING TIMES ........................................... 72
TABLE 8: OVER/UNDER VOLTAGE PROTECTION SETTING AND CLEARING TIME ..................................................... 73
TABLE 9: DG CLASSIFICATION ............................................................................................................................. 90
TABLE 10: UNPLANNED TELECOMMUNICATION FAILURE RATES AND REPAIR TIMES.............................................. 92
TABLE 11: TELEMETRY REPORTING RATES........................................................................................................... 95
TABLE 12: PST AND PLT FLICKER LIMITS ............................................................................................................. 97
TABLE 13: CURRENT HARMONIC LIMITS .............................................................................................................. 98
TABLE 14: INCIDENT LOGGING ...........................................................................................................................109

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1 Introduction

This ―Distributed Generation Technical Interconnection Requirements – Interconnections at
Voltages 50kV and Below‖ outlines the technical requirements to install or modify
Distributed Generation (DG) projects connected to HONI‘s sub-transmission and
distribution (systems at ≤ 50kV) feeders. Technical requirements are defined accordingly to
the size and type of generation. This document is designed to provide an expeditious
interconnection to Hydro One Networks Inc. sub-transmission and distribution system that
is both safe and reliable.

This document, ―Hydro One Networks Inc. Distributed Generation Technical Interconnection
Requirements – Interconnections at Voltages 50kV and Below‖ was prepared by Hydro One
Networks Inc. (henceforth referred to as HONI) to guide generator owners and proponents
in connecting distributed generators (DGs) to HONI‘s distribution and sub-transmission
system. It applies to all interconnecting generators.

The additions of DGs to HONI‘s system introduces changes to the sub-transmission and
distribution system and its response. It is imperative that a technically sound, reliable and
safe interconnection between the DGs and HONI is achieved and this requires diligence
from all parties involved. The requirements in this guideline need to be understood by
designers, consultants, equipment vendors, manufacturers, DG owners, and operators of
the DG‘s and HONI‘s system. These requirements will ensure that the interconnection of
the DG to HONI‘s system will:

 protect the integrity of HONI system and guarantee reliable and quality service to
HONI‘s customers,
 ensure that the interconnection is safe at all times for HONI‘s employees, HONI‘s
customers, DG owners and operators, and for the general public.
 be consistent with the requirements of the OEB and all applicable standards
 meet all of HONI‘s protection, operating and metering requirements.

This interconnection standard has been developed with reference to the Canadian
Standards Association such as C22.3 No. 9-08 – Interconnection of Distributed Resources
and Electricity Supply Systems and international standards such as the Institute of
Electrical and Electronics Engineers (IEEE) Standard 1547 – Draft Application Guide for
IEEE Standard 1547, Interconnecting Distributed Resources with Electric Power Systems.

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This document does not constitute a design handbook. DG owners who are considering
the development of a generation facility intended for connection to HONI‘s system 1 should
engage the services of a professional engineer and/or a registered consulting firm qualified
to provide design and consulting services for electrical interconnection facilities in the
Province of Ontario.

1.1 Scope

This document establishes criteria and requirements for the interconnection of DGs to
the distribution and sub-transmission system. It has been tailored specifically to define
the requirements for connecting DGs to HONI‘s distribution and sub-transmission
system with an operating voltage of 50,000 volts (50kV) or lower. It applies to all
induction generators, synchronous generators and inverter-based generators (solar
photovoltaic, fuel cell, induction generator with a static power converter or permanent
magnet generator with a static power converter). This document contains information
pertaining to HONI‘s system and identifies potential issues, such as protection, safety,
coordination, reliability and operation which shall be considered at different stages of the
project.

Chapter 2, ―Hydro One System Characteristics‖ provides operating characteristics of
HONI‘s sub-transmission and distribution system. It has been included in this document
to ensure that DG owner is aware of HONI‘s sub-transmission and distribution system
behaviour. Chapter 2 contains no requirements for the interconnection of DGs and has
been provided for informational purposes only.

The following sections of this document constitute the requirements that the DG owner
must comply with in order to connect to HONI‘s systems:

 Chapter 3 - DG Technical Interconnection Requirements
 Chapter 4 - Metering Requirements
 Chapter 5 - Connection Process Requirements
 Chapter 6 - Commissioning and Verification Requirements
 Chapter 7 - Maintenance Requirements
 Chapter 8 - Reporting Requirements for DGs

1
This document also applies to DGs connecting to Hybrid Feeders (feeders owned partially by HONI)

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Certain requirements have a separate ―Design Considerations‖ heading which is clearly
defined. This information has been provided for informational purposes to aid in the
design of the DG facility in certain cases and does not represent a requirement. HONI
does not take any responsibility for this information and the engineering consultant
designing the DG facility can decide whether to take the information into consideration
when designing the project.

It is the DG owner‘s responsibility to ensure that all requirements are met. These
requirements have been developed to ensure that HONI‘s sub-transmission and
distribution system is protected from the DG facility. Additional requirements may be
necessary to address unique situations and the DG owner shall be advised of any such
requirements at the appropriate stage.

Certain requirements of this document state that a deviation from the preferred option
(alternative) is available or that certain requirements may be not apply for certain
installations. Any exemptions require written approval from HONI.

This document does not identify any generator protections and the DG Owner shall
ensure that adequate generator protections are installed that will protect the generator
from any situation, including problems originating from HONI‘s sub-transmission and
distribution system.

1.2 Document Reproduction

This document may be reproduced or copied in whole or in part provided that credit is
given to Hydro One Networks Inc. and is not sold for profit.

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1.3 Terms and Definitions

Is defined as…
The Term

ANSI American National Standards Institute

Protection system aimed at detecting islanded conditions
Anti-Islanding (see island) and tripping the DG facility from the distribution
system if an island forms

AVR Automatic Voltage Regulator

BF Breaker Fail
Fault Interrupting Device – may be a breaker, circuit
Breaker
switcher, HVI, LVI
CCRA Connection Cost Recovery Agreement

CEA The Canadian Electricity Association

CIA Connection Impact Assessment

Class 1 DG DG aggregate capacity at PCC < 250kW

250kW ≤ DG aggregate capacity at PCC < 1500kW
Class 2 DG

1.5MW ≤ DG aggregate capacity at PCC < 10MW
Class 3 DG

Class 4 DG DG aggregate capacity at PCC > 10MW

Clearing Time See Trip Time
Central Office – A local telephone company office that
provides a central point for the termination of
CO
telecommunication lines and trunks. And where they can be
interconnected.
CSA The Canadian Standards Association

Dual Element Spot Network – Type of TS
DESN

Distributed Unregulated power generators connected to a distribution
Generation (DG) system through a Point of Common Coupling

Distributed
See Distributed Generation
Generator (DG)

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Distributor The electric utility owning or operating the distribution lines

Any power line facilities under the operating authority of the
Wires owner (HONI or LDC). Distribution power line facilities
Distribution System
usually operate below voltages of 27.6kV nominal, line to
line

See Distributed Generation
DG *Formerly referred to as EG – Embedded Generator

Distributed Generator End Open – A Signal used to confirm
the status of the generator breaker – used to prevent out-of-
DGEO
phase reclosing onto the generator
*Formerly referred to as EGEO – Embedded Generator End Open

DGIT See DG Interconnection Transformer

All equipment including generators, interface transformer,
DG Facility
protections, and line on DG side of the PCC

DG Interconnection The transformer used to step up the voltage from the DG to
Transformer distribution levels

DG Owner The entity which owns or leases the DG facility
Electrical station that is used to step down a sub-
DS transmission voltage to a distribution voltage for distribution
to the end use customer
DSC Distribution System Code

EMI Electromagnetic Interference

ESA Electrical Safety Authority

F Class Feeder Distribution feeder emanating from a HONI DS or HVDS

a single 1 phase or 3 phase line emanating from a
Feeder
substation to supply load

Phenomenon caused by the interaction of system
capacitance and nonlinear inductance of a transformer,
Ferroresonance
usually resulting in very high transient or sustained
overvoltage

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Ground Potential Rise – IEEE defines this as the voltage
that a station grounding grid may attain relative to a distant
GPR
grounding point assumed to be at the potential of remote
earth
Sinusoidal voltages and currents at frequencies that are
Harmonics
integral multiples of the fundamental power frequency
In this document, high voltage refers to HONI system
High Voltage
voltage – can be referred to as medium voltage
HONI Hydro One Networks Inc.

High Voltage Distribution Station – Distribution station
connected directly to HONI transmission system (115kV
HVDS
system). Stepping down transmission voltage to distribution
voltage for distribution to the end use customer

High Voltage Interrupter – any breaker/fault clearing device
that is on the HONI side of the DGIT – voltage rating is
HVI
usually at medium voltage distribution level

Feeders owned partly by HONI and partly by other entities
Hybrid Feeders (e.g. HONI owns the first 50% of the feeder, and an LDC
own the rest of the feeder).
IEEE The Institute of Electrical and Electronics Engineers

IED Intelligent Electronic Device

IESO Independent Electricity System Operator

Interconnection Physical connection of DG to HONI's distribution system
facility which allows parallel operation to occur

Interconnection
See PCC
Point
An operating condition where a DG(s) is (are) supplying
Island load(s) that are not paralleled and synchronized with the
main electric utility (electrically separated)

Local Distribution Company. An entity that owns a
LDC distribution system for the delivery of energy to consumers
from the IESO-controlled grid
The amount of power supplied or required at a specific
Load
location

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Ratio of average load during a designated period to the
Load Factor
peak (maximum) load in the same period

Steady state computer simulation study of voltages and
Load Flow Study
currents in the distribution system
Low Set Block Signal – signal sent over same channel as
DGEO which blocks the Low Set Instantaneous Protections
LSBS
at HONI‘s stations to prevent inadvertent trips due to
transformer inrush during energization.
LVI Low Voltage Interrupter
Medium Voltage See High Voltage

Distribution feeder emanating from a HONI TS – usually ≥
M Class Feeder
24.9kV
Non Detection Zone – range where passive anti-islanding
NDZ protection may not operate within required time due to the
small mismatch between generation and load
NPCC NorthEast Power Coordinating Council

OEB Ontario Energy Board

OESC Ontario Electrical Safety Code

OGCC Ontario Grid Control Centre

The state and operation where the DG Facility is connected
Parallel Operation to the Sub-transmission or Distribution System and
supplying loads along with the electric grid.

PCC Point of Common Coupling

The point where an interconnection system is electrically
Point of Connection connected to the DG facility. Can be the same as PCC.
Refer to Figure 1 for details.

A measure of short-term perception of flicker obtained for a
Pst
ten minute interval

PSS Power System Stabilizer

A measure of long-term perception of flicker obtained for a
Plt
two-hour period

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Protection functions, including associated sensors, relays,
Protection Scheme CTs, PTs, power supplies, intended to protect a distribution
system or interconnected facility

SLD Single Line Diagram

A tendency of a system to oscillate at maximum amplitude
Resonance at certain frequencies, usually resulting in very high voltages
and currents

RLSS Rotational Load Shedding Schedules

Distribution System returning to normal (frequency and
Stabilized voltage) after a disturbance for a period of 5 minutes or as
determined by the Wires Owner

Sub-transmission 27.6kV or 44kV HONI distribution lines

Synchronized See Parallel Operation

Telemeter Transfer of metering data using communication systems

Total Harmonic Distortion – a measurement of the harmonic
distortion present. It is defined as a ratio of the sum of the
THD
powers of all harmonic components to the power of the
fundamental frequency
Temporary Overvoltage – oscillatory power frequency
overvoltages of relatively long duration – from a few cycles
TOV
to hours.
Any power line facilities under the operating authority of the
Transmission
Wires Owner usually operating at higher then 50kV
System
voltages, line to line

A signal sent over communication channels from upstream
Transfer Trip devices commanding the DG to disconnect from HONI's
distribution system

The time between the start of the abnormal condition to the
Trip Time time where the system disconnects and ceases to energize
the distribution system
Electrical station that is used to step down transmission
TS voltage to a sub-transmission voltage for distribution to the
end use customer and DS stations
TT See Transfer Trip

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Test performed on a sample of a particular model/device to
Type Test
verify its operation and design

Wires Owner Utility which owns and/or operates the distribution system

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2 Hydro One System Characteristics

This section describes the characteristics of Hydro One Networks Inc. Distribution System
and identifies aspects that must be taken into consideration when designing a generation
facility that will be interconnected with HONI‘s distribution system. The DG owner must be
able to operate within the ranges specified in this section. In this document, HONI‘s
distribution system may refer to either three phase systems or single phase systems
operating at voltages of 50kV and below – includes systems falling under the definition of
distribution and sub-transmission system. This section contains no requirements for the
interconnection of DGs and has been provided for informational purposes only.

2.1 General Characteristics

Most distribution circuits (feeders) in HONI‘s distribution system are supplied radially
from a single substation (point of supply). In some areas, some feeders may have
alternate points of supply, but will be operated with more than one source of supply only
momentarily during switching operations. HONI‘s distribution feeders operate at the
following voltages (phase-phase/phase-neutral): 44kV (3-Wire), 27.6/16kV, 25/14,4kV,
13.8/8kV, 12.48/7.2kV, 8.32/4.8kV, 4.16/2.4kV.

2.2 System Frequency

The nominal frequency of HONI‘s system is 60Hz. During normal operation (steady
state), the frequency may deviate from 59.3Hz to 60.5Hz, or as supplied by the
transmission system. Under contingencies the frequency deviations may be larger.

2.3 Voltage

The CSA Standard CAN3-C235-83 ―Preferred Voltage Levels for AC Systems, 0 to
50,000V Electric Power Transmission and Distribution‖ provides general guidance for
the steady state service voltage levels on the distribution system. Customers supplied
by the distribution feeder must have adequate voltage levels as per this standard, with
and without distributed generation supplying power for minimum and maximum loading
conditions. The operating voltages found on the distribution feeder vary depending on
load variation, generation variation and contingency situations. Hydro One Networks
standard for voltages on HONI‘s distribution system at the point of delivery during
normal operation is typically in the range of +/- 6% of nominal voltage. The CSA voltage

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standard (summarized below in Table 1) and the voltage levels at the PCC specified in
the CIA report to the DG Owner should be followed by the DG owner.

These values may be exceeded under abnormal conditions. Voltage transients and
swells can occur on the distribution system at any time due to lightning strikes, single
phase to ground faults, and switching, among others. The interconnected DG must be
able to operate within the extreme voltage level variations shown in this document and
must ensure that the insulation levels and protective equipment in their facility can
withstand abnormal voltages on the distribution system.

Table 1: Voltage Limits 0 to 50,000V on Distribution System
Low Limit (% of nominal) Nominal Voltage (%) High Limit (% of nominal)
94 100 106

2.4 Voltage Regulation

HONI utilizes voltage regulating devices throughout the distribution system to maintain
an adequate voltage profile along the feeders and ensure that customers receive
voltages in the range specified in CSA CAN3-235-83. These regulating devices include
line voltage regulators, regulating stations and transformer under-load tap changers at
the Transformer Station (TS) or Distribution Station (DS). HONI operates all voltage
regulating devices on its distribution system to 125V ±1.5V on a 120V base.

The distribution system was designed to correctly operate for unidirectional power flow
(from the substation to the customer). Voltage regulating devices were designed to
correctly operate under these conditions, however, with the addition of DGs into the
system, the power flow can be reversed when the DG is supplying power which may
inhibit the voltage regulators to properly regulate the voltage on the feeder. Due to this,
wherever there is a possibility of reverse power flow, regulating devices (line voltage
regulators, regulating stations and transformer under-load tap changers at the
Transformer Station (TS) or Distribution Station (DS)) on HONI‘s distribution system
shall be changed to suitable devices that allow bi-directional flow.

Steady-state voltage variations at the point of common coupling (PCC) and throughout
the distribution system are limited to +/- 6% of the nominal voltage.

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2.5 Voltage and Current Unbalance

Voltage unbalance due to unbalanced loading and single phase voltage regulation is
typical and inevitable and may reach 2% voltage and 10-20% of total feeder load current
unbalance along certain sections of the feeder, including at the PCC. The DG facility
must not further deteriorate existing unbalanced conditions. In some areas of HONI‘s
distribution system these unbalances may be higher and the DG owner shall contact
HONI to obtain site-specific data. During abnormal conditions such as faults and single
pole reclosing, the unbalance may be very high (current unbalance may be significantly
higher than 20%).

As per NEMA MG 1-1998, the formula for voltage unbalance is:

100 ×(�� )
�� % = (�� )

2.6 Power Quality

In HONI‘s distribution system, all interconnected equipment must comply with HONI‘s
standards for power quality. IEEE Std. 519, IEEE Recommended Practices and
Requirements for Harmonic Control in Electric Power Systems, has been accepted by
industry to provide guidance for appropriate performance and power quality limits such
as voltage flicker and harmonic contribution limits. This standard states that the
recommended practice for utilities is to limit individual frequency voltage harmonics to
3% of the fundamental frequency and the total voltage harmonic distortion (THD) to 5%
on the utility side of the PCC. These limits presented in this standard should be used as
a design criterion when designing the DG facilities as worst case scenario under normal
operation conditions.

2.7 Fault Levels

Fault levels on HONI‘s distribution system vary greatly throughout the system. Factors,
such as location, generation pattern, and contingencies all contribute to varying fault
levels. These fault levels may also change with time as the system expands and new
generation comes online. The DG proponents will receive fault levels for the
distributions system as well as system impedances for a site that is considered from
Hydro One Networks. Maximum allowable fault levels will be provided as well.

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The DG interconnection facilities shall be designed with the fault levels, and maximum
allowable fault levels considered. The X/R ratios must be evaluated for the equipment
selected and the DG facilities shall not increase the fault levels beyond the distribution
system design levels for maximum faults. If the levels increase beyond the existing
design limits, changes to the distribution system equipment will be required.

2.8 System Grounding

HONI‘s distribution facilities are typically operated as uni-grounded (for 3 phase – 3 wire
systems) or multi-grounded (for 3 phase – 4 wire systems). The transformer neutral at
the substation is either solidly grounded (without any impedance) or effectively grounded
through a low impedance at the station (through a neutral reactor, resistor or grounding
transformers) to limit the fault levels on ground faults.

Distribution facility and DG facility grounding shall conform to the Ontario Electric Safety
Code (OESC) and Section 10 of the Canadian Electrical Code.

2.9 Hydro One Networks Inc. Distribution System Feeder Protection

HONI will provide to the DG Owner, upon request, all applicable information about
HONI‘s distribution system protection scheme on the feeder interconnecting with the DG
facility. The general feeder protection scheme utilized on HONI‘s distribution system
where DGs are interconnecting is described below for M Class feeders emanating from
TSs. The feeder protections can be divided into three states:

High Set Instantaneous – Instantaneous protection for close-in feeder faults.
Usually set to the first tap on the feeder. Traditionally employed High Set 50A/50NA
elements. Current HONI standard for feeders with DGs interconnected is to use the
Zone 1 distance (21 – Phase & Ground) element to set the High Set Instantaneous
protection.

Low Set Instantaneous – Instantaneous protection for faults on the entire length of
the feeder. Used primarily as a fuse saving scheme to clear transient faults before
fuse elements start melting. Traditionally utilized using Low Set 50B/50NB
elements. Current HONI standard for feeders with DGs interconnected is to use the
Zone 2 distance (21 – Phase & Ground) element to set the Low Set Instantaneous
protection.

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–
Timed Directionally supervised 51/51N overcurrent elements load/fault
discrimination are used for timed protection of HONI‘s distribution feeders. They are
set to detect and clear faults in their required zone. All timed overcurrent elements
on the distribution system are coordinated with each other to ensure that a minimum
number of customers are affected in the case of permanent faults. For the timed
overcurrent elements to function properly, all DG sources (both positive sequence
and zero sequence sources) need to be removed from the distribution system –
refer to the requirements in Section 3.1.12 – High Voltage Interrupting Device.

F Class feeders, radiating from DSs, have varying levels of sophistication in their
protection schemes. The protections scheme on F Class feeders may need to be
upgraded to accommodate DGs.

2.10 Automatic Reclosing (Fault Clearing)

HONI‘s sub-transmission and distribution system, utilizes automatic reclosing to quickly
clear non permanent faults on the sub-transmission and distribution system, thus,
quickly restoring supply. Generally feeder circuit breakers at Transmission Stations use
single-shot reclosing and reclosers at Distribution Stations and other locations along the
distribution feeder may use single-shot or multi-shot automatic reclosing. Reclosers
may trip a single phase, when single phase loads are connected to the feeder, or all
three phases. If, after the preset number of reclose attempts, the fault persists, the
recloser will lockout and stay open (single phase or three phases will be tripped). The
reclose ―dead time‖ (time that the distribution line is de-energized between reclose
attempts) varies depending on location and type of recloser and can be obtained from
HONI along with all other relevant protection data.

The DG facilities shall be designed with auto-reclosing considered. The generator
protections need to coordinate with the reclosing times of HONI‘s interrupting devices to
ensure that HONI‘s distribution system will not attempt to reclose when the DG is still
connected, risking an out-of-phase reclosing (refer to Section 3 for requirements). If
single phase tripping is employed on HONI‘s distribution system, the DG shall be
designed to protect itself from the unbalance that results. The DG may reconnect to the
system after HONI‘s system voltage and frequency return to nominal and after the
requirements of Section 3.2.19 and Section 3.2.21 of this document are met.

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2.11 Phasing

Conductor phasing may not be standardized and as such, the phase sequence and the
direction of rotation shall be coordinated between the DG proponent and HONI.

2.12 Multiple Source (Networked) System

In some areas of HONI‘s distribution, there may be instances where portions of a
distribution feeder are supplied from two different sources (such as during switching
events). The added complexity in these instances shall be considered when designing
the DG facilities and every precaution shall be taken to ensure that out-of-phase
reclosing does not occur whenever interconnecting to a networked system or a system
capable of source transferring.

The DG facility is required to be removed from service if the source (normal feed) has
changed from the one studied in the CIA and remain disconnected until normal supply
has been restored.

If this requirement changes and multiple sources (alternate feeder) configurations
become available for DGs, this document will be updated to reflect any policy changes.
The DG Owner will be required to have additional protections to alternative feeder
supplies at that time if they wish to have the capability of connecting to alternate
sources.

2.13 Frequency of Interruptions

HONI‘s distribution feeders are mainly unshielded overhead lines spanning vast
distances. They are equipped with insulation levels adequate to withstand expected
voltages. Lighting strikes directly to HONI‘s distribution line result in flashovers of the
insulators on the feeder and result in protection systems tripping the distribution line.
The faults may be temporary in which case a successful reclose will occur (most faults
on overhead distribution lines are temporary in nature), or they may be permanent and
trip the line until repair crews are dispatched and repair the feeder.

Due to the vast distances of the lines and the possibility of frequent momentary trips, the
DG proponent should consider a design that will be suitable for these conditions (such
as auto-restart).

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2.14 Abnormal Conditions

The DG Owner shall consider all possible disturbances which occur on HONI‘s
distribution system while designing their protection system to ensure that HONI‘s
customers and the DG facility are protected. These disturbances can include, but are
not limited to the following:

 Faults on the system
 Frequency excursions
 Partial or complete loss of load
 Transient overvoltages – caused by lightning strikes or switching operations
 Temporary overvoltages
 Single phasing of the three phase system – caused by HONI‘s protection
equipment, switching or broken conductors
 Ferroresonance, overvoltages due to resonance conditions

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3 DG Technical Interconnection Requirements

This ―DG Technical Interconnection Requirements‖ section defines and describes the
technical requirements for the distribution system, and the generation facility (generators
and interconnection equipment as described in the Distribution System Code) for DG
interconnection. The first part, Section 3.1, defines the interconnection technical
requirements, the second part, Section 3.2, defines the protection requirements, the third
part, Section 3.3, defines the control, telecommunications, and monitoring requirements for
interconnected DGs and the fourth part, Section 3.4 defines the performance requirements
such as power quality and reactive power requirements. These requirements need to be
followed in order to connect to HONI‘s sub-transmission, distribution system and hybrid
feeders. In this document, HONI‘s distribution system may refer to either three phase
systems or single phase systems operating at voltages of 50kV and below – includes
systems falling under the definition of distribution and sub-transmission system. They
encourage safe operation and minimize the impact that the DG facility has on HONI‘s
distribution system and in turn to HONI‘s customers. Certain requirements in Section 3 of
this document state that a deviation from the preferred option (alternative) is available or
that certain requirements may be not apply for certain installations. Any exemptions require
written approval from HONI.

Certain requirements have a separate ―Design Considerations‖ heading which is clearly
defined. This information has been provided for informational purposes to aid in the design
of the DG facility in certain cases and does not represent a requirement. HONI does not
take any responsibility for this information and the engineering consultant designing the DG
facility can decide whether to take the information into consideration when designing the
project.

Beyond the requirements presented here in this document, the DG facility must meet all
applicable national, provincial, local and other HONI safety and construction codes. This
guide is intended to provide protection to HONI‘s distribution system and does not cover
protection of the DG facilities. It is the responsibility of the DG Owner to protect its facilities
in a manner that will ensure that events such as outages, short circuits, unbalances,
excessive zero sequence currents and negative sequence voltage, and other disturbances
do not cause damage to the DG facility.

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3.1 Interconnection Technical Requirements

3.1.1 Safety

The DG interconnection shall not create a safety hazard to HONI‘s personnel,
customers, general public and personnel working in the DG facility. Safety is of
primary concern and should be the main consideration when designing the facility.
The primary concern of this document is to provide interconnection specifications
to ensure that safety will be maintained. All equipment shall be approved by the
appropriate authorities (e.g. CSA). The DG facility must have ESA approval prior
to a Distribution Connection Agreement with HONI. The DG facilities must be
maintained throughout the life of the assets to ensure that the DG facility is
operating as designed.

3.1.2 Adverse Effects to HONI Customers

The interconnection of the DG facilities must not materially compromise the
reliability or restrict the operation of HONI‘s distribution system.

The interconnection must not degrade power quality below acceptable levels and if
it is found that it significantly deteriorates the performance of the distribution
system, it shall be disconnected from the distribution system until appropriate
measures are taken to mitigate these negative impacts.

3.1.3 Point of Common Coupling

The Point of Common Coupling (PCC) is the location where Hydro One Networks
distribution facilities (wires) are connected to the DG Facilities or DG proponent‘s
wires and where the transfer of electric power between the DG and HONI takes
place. The PCC must be identified on the single line diagram (SLD), as shown
below in Figure 1.

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Figure 1: Simplified SLD – Shows Clearly Identified PCC

The DG owner is responsible for the design, construction, maintenance and
operation of the facilities and equipment on the DG side of the PCC (all equipment
on the DG side of the PCC shall be approved in accordance with Section 2-004 of
the Ontario Electrical Safety Code) while HONI will coordinate the design,
construction, maintenance and operation of the facilities on HONI‘s side of the
PCC. HONI will carry out the engineering, design and construction required for
additional changes to HONI‘s system in order to facilitate the DG interconnection.
The DG owner may be responsible for the cost of such changes.

In certain instances, either HONI or the DG owner may require that their
equipment be located on the other side of the PCC. If this is the case, the DG
owner must provide the necessary space for HONI to install such equipment and
HONI is to approve this site. A 120V AC power service is to be available.

When specifications and parameters (such as voltage, frequency, and power
quality) are mentioned throughout this document, they must be met at the PCC
unless otherwise stated throughout the document.

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3.1.4 Point of Disconnection

To ensure a means of electrically isolating the DG facility from HONI‘s distribution
system, a means of isolation must be provided (Load Break Switch) and must be in
compliance with the OESC. To conform with recognized standards (this complies
with OESC Rule 84-026, IEEE Standard 1547 Clause 4.1.7 and the Distribution
System Code (DSC) Appendix F.2 Section 1), the disconnect or isolation device
must:

 be a Load Break Switch (capable of interrupting maximum rated load)
 be readily accessible by Hydro One
 be lockable
 have no keyed interlocks
 be Gang Operated (for three phase installations)
 be a Visible Break type
 be of appropriate rating
 be located between the Hydro One system and the DG Facility
 bear warning to the effect that inside parts can be energized when
disconnecting means is open
 be motorized (single phase DG installations exempt)
 have a manual override
 be required to disconnect the DG facility from HONI‘s distribution system
on a breaker fail condition (protection interface for tripping)
 meet all applicable standards and codes (Canadian Electrical Code Part
1 and Part 2)
 be capable of being closed onto a fault with complete safety to the
operator – Must not be a source of injury during operation, even when
closed into a faulted system
 be capable of being operated without exposing the operator to any live
parts.

This point of disconnection is required for the purpose of work protection of Hydro
One and DG facility personnel. Switching, tagging and lockout procedures shall be
coordinated with HONI. The DG Owner and HONI will mutually agree to the exact
location of the disconnect switch. This switch must not be located in a locked
facility and where DG facilities have H2S or any other hazardous materials present,
it shall be located outside of the hazardous area.

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If multiple generators are connected at the DG facility, one disconnect switch must
be capable of isolating all of the generators simultaneously. There may be other
means of meeting this requirement and any proposals must be reviewed by HONI.

3.1.5 Voltage

The DG facility shall ensure that the operation of the DG(s) do(es) not have an
objectionable impact on the voltage at the PCC. The DG owner is responsible for
ensuring that the voltage at the PCC is maintained as per CSA Standard CAN3-
C235-83 ―Preferred Voltage Levels for AC Systems, 0 to 50,000V Electric Power
Transmission and Distribution.‖ Voltage variations at the PCC are limited to +/- 6%
of the nominal voltage under normal operating conditions. Voltages at all load
connections along the feeder must be at least at levels prior to the interconnection
of the DG. HONI will define voltage requirements on a case by case basis in the
CIA. HONI operates all voltage regulating devices on its distribution system to
125V ±1.5V on a 120V base. The introduction of DGs to HONI‘s distribution
system may result in reverse power flow on the feeder. Voltage regulators on
HONI‘s distribution system may require to be upgraded to be capable of handling
reverse flow.

During abnormal conditions, voltage variations may exceed these values. The DG
Facilities must protect themselves from abnormal voltage conditions which the
distribution system is subjected to. These may include voltage transients, sags
and swells caused by lightning, switching, faults, and the loss or switching of
customer loads. Insulation levels and protective equipment must be capable of
withstanding abnormal voltages on HONI‘s distribution system.

The DG should not actively regulate the voltage at the PCC. During normal
operation, the DG must be loaded and unloaded gradually to allow adequate time
for regulating devices on HONI‘s distribution system to respond and avoid
excessive voltage fluctuations.

For DGs connected to HONI‘s 4-wire distribution system, temporary over-voltage
(TOV) that may be caused by the DG facility interconnection should not exceed
125% of nominal system voltage anywhere on the distribution system and under

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no circumstance shall exceed 130%. HONI will advise on action to reduce TOV to
limits.

For power quality parameters such as voltage dip and flicker requirements, see the
Performance Requirements section (Section 3.4).

3.1.6 Voltage and Current Unbalance

Voltage and current unbalance are normal on many distribution feeders as they
supply many single phase loads and thereby all three phases are never equally
loaded. Phase voltage unbalance of 2% and phase current unbalance of 10-20%
of total feeder load is common. Unbalanced loads that result in unbalanced phase
voltages and currents can cause high neutral currents, negative sequence
voltages and currents, zero sequence voltages, thermal overloading of
transformers and 3-phase motors, and can cause protective relaying to mis-
operate.

To protect HONI‘s distribution system and customers, the DG facility must not
further deteriorate existing unbalance conditions at the PCC and the distribution
system. The phase-phase voltage unbalance of three phase DGs must not be
greater than 1% as measured with balanced three phase loading and with no load.
The DG facility should also protect itself from highly unbalanced voltages,
especially when connected to HONI‘s distribution system where single phase
reclosing is used. The DG Interconnection Transformer may supply unbalance
current to support the unbalanced load on the feeder. This unbalance current may
be present even if the generator is out of service. The proportion of unbalance
load current from the DG Interconnection Transformer will vary based on feeder
topology, unbalanced loads, voltage and DG location. During abnormal conditions
such as faults and single pole reclosing, the unbalance may be very high (current
unbalance may be significantly higher than 20%) and it is up to the DG owner to
ensure that the DG facilities are protected from damage due to unbalance.

Single phase DGs connected to a single phase of HONI‘s distribution system are
limited in size (kVA rating) due to the potential impact they may have on
distribution system voltage unbalance (see Section 3.1.9 for size limitations). A
single phase generator must not negatively impact the unbalance of the nearest
three-phase distribution system. Single phase generators shall not cause an

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Hydro One Dg Technical Interconnection Requirements Distribution Interconnections

Hydro One Dg Technical Interconnection Requirements Distribution Interconnections

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