Ian Bradley - APPrO Presentation on DG, Jan 22 2009

8/3/2019 Ian Bradley - APPrO Presentation on DG, Jan 22 2009

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DG Interconnection

Ian Bradley

Manager P&C Programs

Hydro One Networks Inc.January 22, 2009


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Outline

Anti-Islanding Protection

Requirement Transfer Trip Requirement

New technologies being studied

DG Interconnection Transformer New Requirements

Hydro One Feeder Protections

Resynchronization of DG facilities to Hydro One

Example of sequence of events for temporary andpermanent faults

Conclusions


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3

Anti-Islanding Requirement

Islanding of DG facilities shall not be permitted in Hydro Ones

Distribution System

Electric island DG continues to supply HONI customers after

HONI has disconnected via breaker/recloser

TS

F1

F2

F3DG

Recloser/Breaker Closed

DG

CB1

CB2 CB3

CB4

Recloser/Breaker Open


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Islanding of DG facilities shall not be permitted in Hydro Ones

Distribution System

Electric island DG continues to supply HONI customers after

HONI has disconnected via breaker/recloser


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Reasons for Anti-Islanding protection

Prevent Power Quality problems to HONIs customers

Prevent Out-of-Phase Reclosing

Mitigate safety hazards

Solutions will vary depending on size and type of DG

and load profile of feeder

Under/Over Frequency and Voltage protections required.

Directional overcurrent/power, negative sequence overcurrent, zero

sequence voltage, transfer trip may be required


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Transfer Trip Requirement

HONI requires that all exporting DGs be equipped with a Transfer

Trip (TT) signal unless:

the maximum generation is less than 50% of the minimum feeder load not

able to sustain island

Consistent with CSA, international standards & major utility

practices

TS

F1

F2

F3DG

Recloser/Breaker

Transfer Trip


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Transfer Trip Requirement

Transfer Trip may be costly for smaller DG installations especially

when multiple devices need TT to the DG Facility

Hydro One is working on solutions which will replace the Transfer

Trip Requirements for DG facilities interconnecting sized 500kW

and below, which include:

Pulse-based Signaling (Connectivity-based)

Rate-of-change-of-frequency (ROCOF) local based

Vector Surge (Vector Jump) local based

Each technology will be evaluated and tested to determine its

suitability for use as Anti-Islanding Protection for these projects


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DG Interconnection Transformer

(DGIT) Hydro One has initiated a task force of experts to determine the

most efficient, safe and reliable method of connecting generation to

the distribution system

New standards have been created and will apply to all future DG

interconnections

Issues associated with the DGIT:

(HV):(LV) Delta:Wye-Gnd causes damaging temporary overvoltages

to Hydro One during ground faults

(HV):(LV) Wye-Gnd:Delta adds a ground source to system and

desensitizes feeder ground protections

(HV):(LV) Wye-Gnd:Wye-Gnd also acts as a ground source and

allows harmonics to pass


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(DGIT)

3-Wire Distribution Systems

Delta (HV) : Wye-Gnd (LV) DGIT

Grounding transformers may be required on LV side to limit TOV to

DG

Not a ground source will not affect Hydro Ones feeder ground

protection

No TOV on Hydro Ones distribution system

High Voltage Interrupter not a requirement


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(DGIT) 4-Wire Distribution Systems

Wye-Gnd (HV) : Delta (LV)

Neutral reactor required on HV side to limit ground current infeed

Shall be sized to ensure TOV is limited to 125% of nominal will not have a TOV

problem

Is a ground source

For DG installations greater than 500kW, HVI is required to trip DGIT from system

eliminating ground source

For DG facilities smaller than 500kW

Wye-Gnd (HV) : Wye-Gnd (LV) DGIT will be allowed

Does not require HVI

If single phase switching is present upstream three single phase transformers shall be

used


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Hydro Ones Feeder Protections

Hydro One will utilize distance protection for low set instantaneous phase

and ground protection If the low set protections operate, the DGIT and DG shall trip via Transfer

Trip or other approved Anti-Islanding Protections

DGIT is removed from system ground source is also removed

Overcurrent protection will then operate as required DGs will not impede

feeder protections

Using this approach and the combination of DGIT configurations, both

TOV and ground protection problems have been eliminated

May enable quicker connections as standard modules are being developed


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Resynchronization

Following a protection operation, the DGIT shall reclose into the

distribution system within 10 seconds

This will limit the power quality issues associated with DGIT

energization for Hydro One customers

The generator shall stay offline until voltage and frequency has

been stabilized and within limits for at least a period of 5 minutes

If voltage and frequency are not restored within a period of 5

minutes, resynchronization shall lockout and the generators shall

be kept offline until Hydro One operators contact the DG facility

The DGIT and generator reconnection may need to be staggered if

multiple DGs are present on feeder


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Sequence of Events Temporary

Fault

TS

F1

F2

F3

DG

Recloser/Breaker - Open Transfer Trip

Fault Wye

Delta

HVI

Recloser/Breaker - Closed

Fuse (Closed) Fuse (Blown)

Fault Occurs ex. Bird/Tree Contact on a lateral protected by fuse


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Fault

Low Set Instantaneous Feeder Protections senses fault Opens

feeder breaker (Fuse Saving Scheme)

Sends Transfer Trip to DG Facility to HVI and generator breaker


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Fault

TS

F1

F2

F3

DG

Recloser/Breaker - Open

Wye

Delta

HVI

Recloser/Breaker - Closed Transfer Trip


Fault

DGIT and generator breakers open

Fault does not clear


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Fault

Feeder breaker recloses

Fuse blows Fault is cleared Load is Lost


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Fault

DGIT recloses within 10 seconds of breaker reclosing

Generator stays offline

FaultTS

F1

F2

F3

DG


Wye

Delta

HVI




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Fault

Voltage and Frequency is stabilized

Generator resynchronizes after 5 minutes

FaultTS

F1

F2

F3

DG


Wye

Delta

HVI




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Sequence of Events Permanent

Fault

Fault Occurs ex. Conductor breaks


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Low Set Instantaneous Feeder Protections senses fault Opens

feeder breaker

Sends Transfer Trip to DG Facility to HVI and generator breaker


Fault

TS

F1

F2

F3

DG

Recloser/Breaker - Open Transfer Trip

Wye

Delta

HVI

Recloser/Breaker - Closed

Fault


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DGIT and generator breakers open

Fault is not cleared after reclose attempts

Hydro One crews are dispatched to repair line

After 5 minutes the generator resynchronization will lockout


Fault


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Fault

Hydro One repairs line Fault is cleared

Operators close Feeder breaker energizing the line

DGIT recloses within 10 seconds - Generator stays offline


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Fault

Operators contact DG facility

Generators are restarted manually and synchronized to Hydro One


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Summary

The new requirements presented here will allow DGs to connect

with fewer problems, and allow a quicker turn around time.

They have eliminated two of the major technical barriers faced

with interconnection of DGs TOV and feeder protections

Hydro One is working hard to determine best practices and ideal

solutions to technical problems faced with interconnection of

DGs

Focused on safety, reliability, and minimizing cost to DG

Proponents

Creating modular equipment which can be implemented quickly

and efficiently to reduce wait times


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Future

The new DG Interconnection Requirements Standard shall be

provided to the public shortly

Hydro One will continue to develop solutions to enable more

generation and overcome other technical and financial obstacles

such as Anti-Islanding Protection for smaller DGs

P&C Enablement Program for DG Interconnection


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Ian Bradley - APPrO Presentation on DG, Jan 22 2009

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