Fenghai Sui, Miroslav Kostic - Hydro One Network Inc., Canada

Zhiying Zhang - GE Digital Energy, Canada

Zone 2 Distance Protection Coordination

with Distribution Feeder Protection

Texas A&M Relay Conference 2015

Outline

IntroductionCurrent Practices and LimitationsThe Proposed SolutionSimulation TestingConclusions

Introduction

In recent years, renewable energy generators have been widely promoted in OntarioMost of them are connected to Hydro One transmission system at nearby HV transmission linesSuch connections can cause significant increase of the measured apparent impedance due to the infeed effect of the renewable energy sourcesZone 2 reach setting needs to be adjusted based on the maximum apparent impedance in order to cover the entire lineAs a result, LV feeder faults may cause HV transmission line zone 2 operate. Proper coordination is required.

IntroductionS

Equ.Gen.

Equ.Gen.

G11

G12

G21

G22

G24

RJ

CBS CBRCBJ

T

CBL

F1 F2 F24F11

F12 F21 F22 F23G23

Bus

CBF1 CBF2

IntroductionS

Equ.Gen.

Equ.Gen.

RJ

CBS CBRCBJ

Equ.Gen.

Zsj Zrj

Is IrIj

Us

Uj

𝒁𝒂𝒑𝒑=𝑼𝒔𝑰𝒔 =

𝑰𝒔∗ (𝒁𝒔𝒋 )+ ( 𝑰𝒔+𝑰𝒋 )∗𝒁𝒓𝒋𝑰𝒔 =(𝒁𝒔𝒋+𝒁𝒓𝒋 )+ 𝑰𝒋

𝑰𝒔 ∗𝒁𝒓𝒋=𝒁𝒔𝒓 + 𝑰𝒋𝑰𝒔 ∗𝒁𝒓𝒋

The apparent impedance consists of two parts: 1) Line impedance Zsr2) An additional part due to the tapped

generation

Introduction

C1

C2

This will cause some coordination issues

Apparent impedance measured at bus S can be much bigger than the line impedance Zsr due to infeed effectThe large apparent impedance will result in large zone 2 reach setting

Problem

The zone 2 element may operate on a fault beyond direct adjacent lines. This issue may be solved with additional time delay.The zone 2 element may pick up under heavy load condition. This issue may be solved with load encroachment feature embedded in IED.The zone 2 element may pick up faults on LV bus or LV feedersIn this paper, only this problem is discussed and

addressed

Current Practices

Building a new switching station

Current Practices

Splitting one large step-up transformer into two smaller transformers

Current Practices

Multi-terminal current differential protectionS

Equ.Gen.

Equ.Gen.

G11

G12

G21

G22

G24

RJ

CBS CBRCBJ

T

CBL

F1 F2 F24F11

F12 F21 F22 F23G23

Bus

CBF1 CBF2

87L

Proposed Solution

A method has been developed by using programmable logic within a modern digital relayIn this method, the timed zone 2 distance protection is automatically switched to a short delay or a long delay based on the operation sequence and timing conditionDistance zone 2 element will provide regular protection to the transmission line faults as usual, and also provide coordinated backup protection to the distribution feeder faults

Proposed Solution

No additional communication is required within this solutionCompared to current practices, it’s a cost saving solution. High capital investment can be avoided.The proposed solution has been verified with fault simulations on both HV transmission lines and LV feeders

Zone 2 Setting Review

Pilot Schemes

Pilot schemes are also employed in Hydro One grid, most commonly POTT and DCBIn order to avoid maloperation of the pilot scheme on the LV feeder fault, a blocking signal is required to be sent to the terminal station from the tapped station

SEqu.Gen.

Equ.Gen.

RJ

CBS CBRCBJ

T

CBL

F1 F2 F24F11 F12 F21 F22 F23

BusCBF1 CBF2

LV Feeder Protection and Auto-reclose

Main feeder protection

Sub-feeder or branch protectionSub-feeder or branch protection

SEqu.Gen.

Equ.Gen.

RJ

CBS CBRCBJ

T

CBL

F1 F2 F24F11 F12 F21 F22 F23

BusCBF1 CBF2

LV Feeder Protection and Auto-reclose

Zone 2 Operation Sequence

For a transient LV feeder fault, the zone 2 element picks up and drops down after the fault is cleared by LV feeder protectionFor a permanent feeder fault, the zone 2 element picks up and drops down for a certain period and then picks up again for a longer periodFor a fault on HV transmission line, the zone 2 element will continuously pick up before CB is open

Proposed Solution – LogicLogic below is designed for zone 2 distance protection to properly coordinate with feeder protection and avoid mis-operation for faults on LV feeders

Proposed Solution – Logic Implementation

Simulation – Transient Fault on LV Feeder

Z2

GA1-1

GA1-2

GA1-3

DT-2

T2-2

10 seconds

50ms 400ms

Falling edge

Fault is cleared by feeder protection, Z2 resetFeeder reclose successfully

Simulation – Permanent Fault on LV Feeder

Z2

GA1-1

GA1-2

GA1-3

DT-2

T2-2

50ms 400ms50ms 400ms

10 sec.

Fault is tripped by

feeder protection587ms

Breaker Dead Time

Reclose to a permanent faultT2-2 is high

Timed Z2 did not operate on LV permanent fault

Simulation – Permanent Fault on HV Feeder

Z2

GA1-1

GA1-2

GA1-3

DT-2

Other Protection Trip

50ms 400ms50ms 400ms

25ms

520ms

GA2-3

GO1-1 400ms

Never see a falling edgeDT-2 keeps low

Breaker Dead Time

Reclose to a permanent fault

Fault is intentionally held for 520ms though other protection has operated.

SummaryThe large zone 2 protection reach setting value may result in that the timed zone 2 protection operates on a permanent LV feeder fault

A solution has been proposed in this paper to deal with coordination issue between timed zone 2 protection of HV transmission line and LV feeder protection

It is a cost-saving method. High capital investment, such as building switching stations, is not required.

The requirement of this solution is that the protection relay must have flexible programming logic capability

Thank You

Questions?