Copyright © SEL 2012

Analysis of Selected Motor Event and Starting Reports

Derrick Haas, Jason Young, and Ryan McDaniel

Schweitzer Engineering Laboratories, Inc.

Discussion Topics

• Introduction

• Motor start and mechanical problem

• Current unbalance

• Self-balancing differential

• RTD protection

Discussion Topics

• Full phase differential

• Loss of field

• Self-clearing fault

• Conclusions

Introduction

• More than 85% of load for industrial users

• Response to failure – repair versus replace

• Root-cause analysis

• Event reports, motor trending data, load trending data

Event 1: Event Report

Motor Start Report (MSR) C

urre

nt (A

) or T

herm

al C

apac

ity U

sed

(per

cent

• 10

)

1800

1000

1400

00 10 50403020

1600

1200

200

400

600

800

60Time (s)

IA IB IC TCU • 10

Time Versus Current Plot

Current (• FLA)

Tim

e (s

)

100

10

1

0.12 3 7654

Motor Thermal Limit Curve Relay Curve #3 Motor Starting

Current

MSR From September C

urre

nt (A

) or T

herm

al C

apac

ity U

sed

(per

cent

• 10

)

1000

1400

00 10 50403020

1600

1200

200

400

600

800

60Time (s)

IA IB IC TCU • 10

Summary of MSRs

Report Date Start Time (s)

Maximum Current (A)

MSR5 9/30/10 13.3 1,446

MSR4 10/12/10 15.5 1,492

MSR3 12/15/10 15.1 1,531

MSR2 12/15/10 11.3 1,506

MSR1 12/15/10 15.3 1,515

MSR With Curve = 4 C

urre

nt (A

) or T

herm

al C

apac

ity U

sed

(per

cent

• 10

)

1000

1400

00 10 50403020

1600

1200

200

400

600

800

60Time (s)

IA IB IC TCU • 10

Event 2: Phasor View

45 degrees

90

225

135

180

270

315

0

45IB(A)VBC(V)

VCA(V)

VAB(V)

IA(A)

IC(A)

Relay Settings

• CT ratio = 50:5 (10)

• FLA = 38.9 A primary

• Negative-sequence pickup = 0.5 • FLA

• Negative-sequence definite-time delay = 0.1 s

• Current unbalance 46 pickup = 20%

• Current unbalance time delay = 5 s

Negative-Sequence Overcurrent TRIP

Event 3: Self-Balancing Differential C AB

16,000 hp Motor

87A

87B

87C

50:5

50:5

50:5

Conduit From Motor to Switchgear

Relay in Switchgear Door

Filtered Event Report

Raw Event Report

Diagram With Short-Circuit Locations C AB

16,000 hp Motor

87A

87B

87C

50:5

50:5

50:5

Conduit From Motor to Switchgear

Relay in Switchgear Door

Report After Correction

Event 4: RTD Trending Data

RTD1 RTD2 RTD4 RTD5 RTD7 RTD8

Tem

pera

ture

(°C

)250

50

70

90

110

130

150

170

190

210

230

16:40 21:40 2:40 7:40 12:40 17:40 22:40 3:40 8:40 13:40 18:4023:40 4:405/20 5/21 5/22 5/23

Time of Day

RTD 1 RTD 2 RTD 4 RTD 5 RTD 7 RTD 8

Event 5: Event Report

A-Phase Currents P

rimar

y C

urre

nt (A

)

–4000

–3000

–2000

–1000

0

40003000

2000

1000

1514131211109876543210Time (cycles)

Winding 1 AWinding 2 A

B-Phase Currents P

rimar

y C

urre

nt (A

)

–4000

–3000

–2000

–1000

0

40003000

2000

1000

1514131211109876543210Time (cycles)

Winding 1 BWinding 2 B

C-Phase Currents P

rimar

y C

urre

nt (A

)

–4000

–3000

–2000

–1000

0

4000

3000

2000

1000

1514131211109876543210Time (cycles)

Winding 1 CWinding 2 C

Solution 1: Time Delay

IN1600

0X Timer

XT

87R(Differential)

MTU3 (Trip 3to lock out relay)

MTU1 (Trip 1for event reports)

87U(Unrestrained

differential)

Solution 2: Adjust Sensitivity

Replay With Settings Change

Event 6: One-Line Diagram

Motor Relay

87

Generator Relay

yM

x

Event Report

Normal Load Phasors 90

225

135

180

270

315

0

45

IBX(A)

VBCX(V)

VCAX(V)

VABX(V)

IAX(A)

ICX(A)

90

225

135

180

270

315

0

45

IBX(A)

VBCX(V)

VCAX(V)

VABX(V)

IAX(A)

ICX(A)

Phasors During Loss-of-Field Event

Event 7: Relay A Event Report

Relay B Event Report

-400

-200

0

200

400

600

800

1000

1200

1 4 7 10 13 16 19 22

–

–

Cycles

Cur

rent

(A)

IA IB IC IA Differential IB Differential IC Differential

Closer Look at Relay A Event Report

14,000 hp Motor

Incoming and Neutral Conductors

C-Phase Neutral Conductor

Top View of Conductors

C-Phase Incoming Conductor

C-Phase Neutral Conductor

C-Phase Incoming Conductor

Area of Deep Insulation Erosion

10 Inches of Visible Tracking Seen in the C-Phase Incoming Conductor

Ground Point

C-Phase

Neutral Conductor

Burn Mark to Ground

Fault Representation A CB

14,000 hp Motor

Moisture

Ground Connection

Conclusions

• False trip or failure of a motor can halt a process

• Event reports should be analyzed in detail, regardless of company replacement policy for motors

• Lessons learned from event reports can be used to make operations safer and more reliable

Questions?