Microprocessor Relay ProtectionJasvinder Blah

&Naveen Manikarnika

Agenda

• Transformer Protection• Electromechanical Relays• Microprocessor Relays• Relay Characteristics & Testing

got relays?

Relay Protection

• What is Relay Protection?• Typical transformer protection:

51N87 51V

59 67 87N

Primary Protection - 87

Kirchhoff's Current Lawi1

i2 i3

i4

𝑖1+𝑖2+𝑖3=𝑖4

Transformer Protection

BKR(3) 3000/5A (3) 3000/5A

To 13kV Bus

Transformer: 68kV/13.8kV

Electromechanical Relays

Microprocessor Relays

Microprocessor Relays

ADVANTAGES• All elements and phases in

one box• Self-checking and alarm• Internal compensation• Oscillography and SER• Direct Tripping

DISADVANTAGES• Technology advancing in a

fast pace• Firmware defects/upgrades

11

Delta - Wye

IAB

IBC

ICA

Ia’

Ib’

Ic’

30º

Secondary Currents Lags the Primary by 30 DegreesA

B

Ca’

b’

c’

A

B

C

Ia’

Ic’

Ib’

Electromechanical CT Compensation

Microprocessor CT Compensation

CT Compensation

Internal Phase Compensation

A

B

C

-Ib’

Ia’

Ic’

Ib’

30º

Ia’-Ib’

Ia(Comp) =

Ib(Comp) =

Ic(Comp) =

3

)(

3

)(

3

)(

''

''

''

ac

cb

ba

II

II

II

Ia(comp)

Transformer Protection with Microprocessor Relays

BKR

87 51N 51V

59 67 87N

(3) 600/5A (3) 3000/5A

(1) 1200/5A

(3) CCVTs72.5kV/67.08V

(3) PTs14,400V/120V

Incoming 69kV Feeder To 13kV Bus

Transformer: 68kV/13.8kV

SEL-487E

0 0.6 1.3 2 2.4 2.8 3.2 3.6 5 6 7

0

0.5

1

1.5

2

2.5

3

3.5

I Restraining

I Ope

ratin

g

Restraint Region

Operating Region

Unrestrained Differential

87 Percent Differential

Exten

ded S

ecurit

y M

ode

87 Testing

0 0.6 1.3 2 2.4 2.8 3.2 3.6 5 6 7

0

0.5

1

1.5

2

2.5

3

3.5

I Restraining

I Ope

ratin

g

Restraint Region

Operating Region

Unrestrained Differential

Microprocessor Relay Testing

Dual RS-232

Output Contacts

Current Inputs

Voltage Inputs

A B C A B C

87 – Differential

BKR

87 51N 51V

59 67 87N

(3) 600/5A (3) 3000/5A

(1) 1200/5A

(3) CCVTs72.5kV/67.08V

(3) PTs14,400V/120V

Incoming 69kV Feeder To 13kV Bus

Transformer: 68kV/13.8kV

SEL-487E

Initiate DTT

Initiate BKR Failure Timer

Pop Quiz !!!

87N – Neutral Differential

BKR

87 51N 51V

59 67 87N

(3) 600/5A (3) 3000/5A

(1) 1200/5A

(3) CCVTs72.5kV/67.08V

(3) PTs14,400V/120V

Incoming 69kV Feeder To 13kV Bus

Transformer: 68kV/13.8kV

SEL-487E

Initiate DTT

Initiate BKR Failure Timer

51N – Neutral Overcurrent

BKR

87 51N 51V

59 67 87N

(3) 600/5A (3) 3000/5A

(1) 1200/5A

(3) CCVTs72.5kV/67.08V

(3) PTs14,400V/120V

Incoming 69kV Feeder To 13kV Bus

Transformer: 68kV/13.8kV

SEL-487E

Trip Bus-Tie Breaker

51V – Voltage Controlled Overcurrent

BKR

87 51N 51V

59 67 87N

(3) 600/5A (3) 3000/5A

(1) 1200/5A

(3) CCVTs72.5kV/67.08V

(3) PTs14,400V/120V

Incoming 69kV Feeder To 13kV Bus

Transformer: 68kV/13.8kV

SEL-487E

Trip Bus-Tie Breaker

67 – Directional Overcurrent

BKR

87 51N 51V

59 67 87N

(3) 600/5A (3) 3000/5A

(1) 1200/5A

(3) CCVTs72.5kV/67.08V

(3) PTs14,400V/120V

Incoming 69kV Feeder To 13kV Bus

Transformer: 68kV/13.8kV

SEL-487E

Initiate BKR Failure Timer

59 – Zero Sequence Overvoltage

BKR

87 51N 51V

59 67 87N

(3) 600/5A (3) 3000/5A

(1) 1200/5A

(3) CCVTs72.5kV/67.08V

(3) PTs14,400V/120V

Incoming 69kV Feeder To 13kV Bus

Transformer: 68kV/13.8kV

SEL-487E

Initiate BKR Failure Timer

Testing Challenges

• Breaker Failure– Time delay for all elements– Perform testing without disabling elements– Requires some creativity

• Utilize 2nd Harmonic Block to disable 87

2nd Harmonic Block

Fault Playback

• Play fault back to the relay• Useful for investigations• Fully functional test• Oscillography/SER

Oscillography

Future

• 61850 (GOOSE)• Merging Units• Optical CTs• Sample Values

Conclusion

• Evolution of relay protection• Challenges

– Training and learning curve – Cybersecurity

Questions?