Protection Considerations for Installation of Distributed Energy Resources

Jerry Johnson – Basler Electric CompanyTexas A&M Protective Relaying Conference

March 31, 2015

Introduction

- Paper is tutorial in nature- Discusses evolving technologies- Discusses evolving intertie standards- Applied to distribution, mostly radial- Solar by far the fastest growing- Inverter-based installations- Standby applications are synchronous

Introduction

- Screening process for parallel operation- Higher Gen capacity, involve Protection Eng- Area EPS Web site procedures- Safety of personnel on both sides of PCC- Consult IEEE 1547 family of standards

Commonly Used Terms

- DER: Distributed Energy Resource- EPS: Electric Power System - Local EPS: Local Electric Power System - Area EPS: Area Electric Power System- PCC: Point of Common Coupling- Island: Local EPS carries Area EPS Load

• Unwanted • Planned

Types of DER

- Peak shaving: Reduce load demand• “32” at PCC prevents power flow to Area EPS

- Net Energy Metering• Area EPS monitors energy flow into or out of a facility• Customer is either billed or reimbursed based on Net

- Export Energy• Area EPS contracts with DER or local EPS• Based on Area EPS tariff • Area EPS purchases power

Types of Generation

- Synchronous- Induction

• Excitation from the system• Excitation from capacitor banks• Doubly fed

- Power inverters• DER inverter-based photovoltaic systems are the

fastest growing.

Types of Generator Connection

- Large generator connection transmission• Operated similar to utility generation

- 10 MVA DER connection to distribution• Follows IEEE 1547-2003 and Area EPS guidelines

Large Generator -Transmission Tie

G69 kV

and above

Utility Grid

Other Plant Loads

Point ofCommon Coupling

(PCC)

Point ofCommon Coupling

(PCC)

DER on Radial Distribution

69 kV and above

Utility Grid

Transmission Distribution

DER

Tapped toTapped toRadial Distribution

Circuit

13kV and below

Radial Lines

Typical DER Connection to Radial Distribution Feeder

Local Load

Radial Distribution Feeder

OR

G

Utility

R

Intertie Transformer

PCC

Standard IEEE 1547-2003

- Subjects not included in IEEE 1547-2003• How the intertie should be operated• How to protect the generator• Capacity greater than 10 MVA (today)• Closed transitions of less than 100 ms

Standard IEEE 1547-2003

- Subjects included in IEEE 1547-2003:• DER shall cease to energize for faults on the utility.• Cease to energize unintentional islands within two sec• Additional requirements

› Synchronizing› Power Quality› Testing› Commissioning

Evolving IEEE 1547-2003

- IEEE1547a Approved June 2014• Voltage regulation• Voltage and Frequency Ride Through

- P1547.1a in balloting process- P1547-2003 full revision began March 2014

Intertie Protection Small DER

Local Load

Radial Distribution Feeder

OR

G

Utility

R

Intertie Transformer

PCC78V27 VT

81ROC59 81U 81O

Local Load

Radial Distribution Feeder

G

Utility

R

Intertie Transformer VT Anti-Islanding

Equipment Protection

OR

27 59 81O78V 81U81ROC 47

32 46 67 51

Customer Fault Protection

59N

TF and Utility Fault Protection

PCC

25

25

Intertie Protection, Larger DER

Challenge Basic Islanding Protection

UTILITY

1-PT

3-PT

3 -CT

27/5981

ROCPCC

G

78V 81O/U

Challenge Islanding – T.T.

DER

52/b

UtilityBus

TransferTrip

Transmit

UtilityFeeder

TTRec.

Trip

Challenge DER Fault Current Source

FaultUtility Bus Utility Feeder

3000 Amps

2000 Amps

5000 Amps

DER

X

Challenge - Fault Current

FaultUtility Bus Utility Feeder

DER

67

3-VT

3-CTOr 51/27C or

51/27R or21

X

Challenge-TX Connection

FaultUtility Bus Utility Feeder

DER

Primary Deltaor UngroundedWye

X

Phasors without Islanded DER

Vag

VbgVcgNormal

Vag

VbgVcgWith A-g fault

DG Islanded with Ungrounded Primary

Vag

VbgVcg

Utility Breaker Open

Ground Van

VbnVcn

Vag = 0Vbg = VbaVcg = Vca

With A-g fault

59N for Ungrounded Primary Protection

Utility Bus

59N

VTs

a

a

a

b

b

b

3 V0

c

c

c RES

Challenge TX Grounded Primary

Utility Bus Utility Feeder

DER

Ground Fault

Grounded Wye - PriDelta - Sec

X

Challenge TX Primary Grounded

Local Load

Radial Distribution Feeder

G

Utility

R

Intertie Transformer

VT Anti-Islanding

Equipment Protection

78V27 81

ROC59 81O 81U 47

32 46 67 51

Customer Fault Protection

TF and Utility Fault Protection

51N

50/51

67

PCC

A

B

Challenge TX Primary and Secondary Grounded Wye

GG

rroo

uu

nn

dd

ee

dd

WW

yy

ee

3I 0

Fault

Utility Bus Utility Feeder

DER

Ground FaultX

X

Summary

- DER on distribution feeders - popular alternative for renewable power assets.

- Standards continue to evolve providing informative, uniform requirements for advancement of DER technology.

- The Area EPS has responsibility to ensure the safe, reliable operation of distribution systems.

Summary

- DER installations will continue to present protection challenges for ensuring safe and reliable power system operation.

- Continuing improvement of uniform standards and effective screening processes will help meet these challenges.

Thank you.

Questions