The effects of voltage sags For IEEE

The effects of voltage sags • For IEEE Hong Kong Section • May 31, 2002 by Terry Chandler Power Quality Inc/Power Quality Thailand LTD May 2002 WWW. powerquality. org All rights reserved 1

Sags or Dips? A decrease in the nominal voltage for a short duration. May 2002 WWW. powerquality. org All rights reserved 2

Standards regarding Sags • IEC 1000 -4 -1/11 Measurement of sags • IEEE 1159 Monitoring of Sags • IEEE P 1346 • ANSI C 84. 1 • IEEE 1100 May 2002 WWW. powerquality. org All rights reserved 3

IEEE SCC 22 • Short duration variations • 2. 1 Instantaneous – 2. 1. 2 Sag(Dip) 0. 5 to 30 cycles 0. 1 to 0. 9 pu • sags (dips) have a magnitude and duration • SCC is the standard coordination committee of IEEE May 2002 WWW. powerquality. org All rights reserved 4

Accepted description • Sag is a IEEE term DIP is IEC term • Sag refers to % of decrease in Voltage – IE a 20% sag is a voltage decrease to 0. 8 PU • DIP refers to % of voltage remaining – IE a dip to 80% is a decrease to 0. 8 PU • Is the glass half full or half empty? May 2002 WWW. powerquality. org All rights reserved 5

Classifying Sags (Dips) • CBEMA • 100% May 2002 WWW. powerquality. org All rights reserved 6 • 1 day

Classifying sags (dips) II • ITIC (New CBEMA) • acceptable May 2002 WWW. powerquality. org All rights reserved • unacceptable 7

Cause of Voltage sags • Faults on the distribution system • User distribution system failure • User loads • Equipment malfunction May 2002 WWW. powerquality. org All rights reserved 8

Faults on the distribution system May 2002 WWW. powerquality. org All rights reserved 9

User equipment that can cause sags • Copiers and laser printers • Arc welders • Motor starting • Power saws May 2002 WWW. powerquality. org All rights reserved 10

Welder causes voltage sag May 2002 WWW. powerquality. org All rights reserved 11

Voltage sag from the utility May 2002 WWW. powerquality. org All rights reserved 12

Semi 47 Voltage sag standard • A new standard developed by the SEMI organization members to define the desired minimum equipment sensitivity to voltage sags • Similar to ITIC curve in the voltage sag domain May 2002 WWW. powerquality. org All rights reserved 13

ITIC Semi 47 May 2002 WWW. powerquality. org All rights reserved 14

ITIC 47 Semi | 10 sec | 0. 5 sec 20 ms • 50 ms 0. 2 May 2002 WWW. powerquality. org All rights reserved 15 0. 5 second

Load sensitivity to voltage sags • Motors – Contactors that Small 50% sag shuts down 600 hp load May 2002 WWW. powerquality. org All rights reserved 16

Sag indications without a PQ meter • Lights blink • Motors slow down and return to normal speed • Computers reboot unexpectedly • Automated equipment stops unexpectedly May 2002 WWW. powerquality. org All rights reserved 17

Root cause of sensitivity • Electrical contactor on the input power May 2002 WWW. powerquality. org All rights reserved 18

Process sensor • With voltage sags sends shut down signal May 2002 WWW. powerquality. org All rights reserved 19

Emergency shutdown circuit • With voltage sag sends shutdown signal May 2002 WWW. powerquality. org All rights reserved 20

DC buss sag May 2002 WWW. powerquality. org All rights reserved 21

Voltage imbalance sensor May 2002 WWW. powerquality. org All rights reserved 22

Improving voltage sag immunity • Relay settings • DC relays • Switchmode power supply configuration • oversize power supply or capacitor • Dynamic sag corrector • Connect loads phase to phase May 2002 WWW. powerquality. org All rights reserved 23

Voltage sense relays • Upper and lower trip points May 2002 WWW. powerquality. org All rights reserved 24

Ride thru device May 2002 WWW. powerquality. org All rights reserved 25

Sag mitigation technologies • UPS – Standby – line interactive – On-Line • Dynamic voltage restorer (DVR) • Voltage Regulator • Static transfer switch May 2002 WWW. powerquality. org All rights reserved 26

UPS Uninterruptible Power Supplies • Battery – On-line – Standby • Flywheel • Super conductor • Super Capacitor • Fuel Cell May 2002 WWW. powerquality. org All rights reserved 27

On-line UPS May 2002 WWW. powerquality. org All rights reserved 28

Rotary UPS May 2002 WWW. powerquality. org All rights reserved 29

Example of rotary May 2002 WWW. powerquality. org All rights reserved 30

DVR May 2002 WWW. powerquality. org All rights reserved 31

Flywheel ups May 2002 WWW. powerquality. org All rights reserved 32

Example of flywheel UPS May 2002 • Photo compliments of Beacon. com WWW. powerquality. org All rights reserved 33

Standby UPS • Battery or Flywheel • More efficient than on -line • Output meets ITIC or Semi-47 standard May 2002 WWW. powerquality. org All rights reserved 34

Standby UPS May 2002 WWW. powerquality. org All rights reserved 35

Example of Standby UPS May 2002 WWW. powerquality. org All rights reserved 36

• 3 phase sag May 2002 WWW. powerquality. org All rights reserved 37

• UPS output during sag May 2002 WWW. powerquality. org All rights reserved 38

Conclusions • Voltage sags are the #1 Power Quality problem • The source can be from the utility or from internal loads, wiring, problems etc • Solutions can be very inexpensive or very expensive May 2002 • WWW. powerquality. org All rights reserved Graph compliments 39 of WWW. powerstandards. com

The bottom line • Voltage sags are an economic or $$ problem • It requires detailed PQ data to determine if the solution costs $100 or $10, 000. May 2002 WWW. powerquality. org All rights reserved 40