Copyright © SEL 2016

Apply Travelling Wave in Power System Protection and Operation

Edmund O. Schweitzer, III Bogdan Kasztenny Armando Guzmán Veselin Skendzic Venkat Mynam

Schweitzer Engineering Laboratories, Inc.

•  Traditional models are steady-state •  The “forcing functions” are at 60 Hz •  Instrument transformers are rated at 60 Hz • CCVTs are “band-pass” devices at 60 Hz

Phasor-Based Protection Makes Sense

Determining steady state takes time. Shorter windows are faster but less accurate than full cycle.

Speed of Present-Day Relays

–1 0 1 2 3 4 5–20

–15

–10

–5

0

5

10

15

Time, cycles

Cur

rent

, pu

Ope

ratin

g Ti

me

in C

ycle

s

Fault Location in Percent of Set Reach

Line-to-ground fault, SIR = 1.0

Modern Distance Relays: 8–16 ms

0 10 20 30 40 50 60 70 80 90 0

0.5

1

1.5

100

•  Increase power system stability • Allow more power transfer • Enhance public and utility personnel safety •  Limit equipment wear •  Improve power quality • Reduce property damage

Quest for Ultra-Fast Relay Operation

15 MW more per millisecond saved R. B. Eastvedt, BPA, 1976 WPRC

The Need for Speed Moving Energy at the Speed of Light

Safer • Less Damage • Improved Dynamics

ASEA RALDA (1976) 5 ms Directional Wave Relay

−

B

Di Dv Di Dv− + −

+ + − +

A

BBC LR-91 (1985) 5 ms UHS Directional Relay

Fault is forward when the operating point enters the 2nd or 4th quadrant

Why Today? The Need for Speed

Faster communications Powerful processors Better simulations

May be simpler

Waves Travel Toward Line Terminals

vRvSiRiS F

Practical Traveling Wave Relaying Build on TWFL Experience

Single-ended: sort out reflections; easier with voltages Two-ended:

Directional comparison Current differential

Speed of Light Limits Relay Time

The fastest communications path is the line

S R100-mile line ≈ 600 µs X

300 µs 300 µs

600 µs by line or 1,000 µs by fiber

900 µs or 1,300 µs

Propagation Adds Up to 1.6 ms What Are Other Delays?

Propagation 1.6 ms Signal processing 0.5–2 ms POTT processing 0.1 ms TRIP output 0.1 ms TOTAL: 2.3–3.8 ms Then, it’s up to the circuit breaker

Speed Limiters and Options

Circuit breaker 17 ms Solid state? Auxiliary relay 4 ms Don’t use

Contact input delay 1 ms Improve signaling Process bus 1.5 ms Hard wire

Fast Hardware for < 4 ms Tripping

The time to trip is determined by propagation and processing… NOT by the 16,667 µs duration of a cycle

Component TimeDomain,μs Today,μs Sampling period 1 > 100 Processing interval 100 1,000–2,000 Trip outputs 10–100 4,000 Digital trip outputs 100–1,000 1,000–4,000 Channel interface 50–1,000 2,000–8,000 Data sharing 50–1,000 100,000

TD21 §  Underreaching (Zone 1) §  Communications-independent

POTT §  TD32 and TW32 for direction §  Fast MIRRORED BITS® communications as a teleprotection channel

TW87 §  Current-only §  Direct fiber as a channel (100 Mbps) §  GPS-independent

Modern TW Relay: Speed With Security

•  Inherently FAST principles for 32, 21, 87 for 2 to 4 millisecond trip times

•  Easier to set and understand •  Inherently secure for LOP •  Suitable for single-pole tripping •  Inherently suitable with series compensation •  Addresses the need for speed

Breaking Free of Phasor Limitations Energy Moves at the Speed of Light