21 st Century Facilities

Transcription

1 Electrical Testing

2 21 st Century Facilities Facility Owners face tough challenges 24 X 7 reliability needed Non linear loads cause harmonics VFD Computers Switching transients disrupt operations Less customer support from Utilities Pressure to hold energy costs down Compressed schedules for expanding facilities Effect of EMF on computers and equipment How to expand facilities to meet customer needs cost effectively Harsh environments

3 Formula For Successful Facilities Facility Planning and Scheduling Engineering Design Quality Installation Acceptance Testing Regular and Complete Maintenance Preventative Maintenance Testing

4 Testing for All Phases of Facility Improvements Load analysis for facility improvements Trouble shooting and correction of problems Acceptance Testing for New Projects Switchboards and/or Switchgear Circuit Breakers Preventative Maintenance Forensic Testing

5 Testing Load Analysis Measuring existing loads with portable test equipment 120V to 480V, Amps Recorded values Volts - Power Factor Amps - KVA KW - KVAR Measure harmonic distortion THD - Voltage & Current Individual harmonics Measure loads for emergency generator sizing Motor starting studies

6 CURRENT Trend Monitoring Trend Plot For Device: 3 Phase Current IAvg IA :50 AM 11:00 AM 11:10 AM 11:20 AM 11:30 AM 11:40 AM 11:50 AM 11/5/01 10:50:00 AM to 11/5/01 11:50:00 AM IB IC

7 Testing Acceptance Testing Equipment Acceptance Testing Medium Voltage Transformers Switchgear Cables PFC Air Switches SF6 Circuit Breakers Below 600V Switchboards and Switchgear Motor Control Centers Generator Load Testing

8 Acceptance Testing Cont d. Short Circuit and Coordination Studies Short Circuit Study verifies overcurrent protective devices meet requirement for interrupting available fault current. Coordination Study graphically shows how overcurrent protective devices coordinate to have the CB closest to the fault open. Ground Resistance Testing 3 Point Fall of Potential Method Ground Fault Interruption Testing Required by NEC

9 Transformer Testing Oil Filled Transformers On Line, no shutdown Excellent analytical technique developed by IEEE to evaluate condition of transformer IEEE/ANSI C57 Distribution, Power and Regulating Transformers. C is the Standard for Interpretation. NFPA 70B Section Oil Tests Section Dissolved Gas Analysis

10 Transformer Testing Cont. d Mineral Oil is complex hydrocarbon molecular compound At normal conditions it is very stable Heat, corona and arcing break molecule down to sub elements (combustible gases) (H 2, CH 4, etc.) Analysis of dissolved combustible gases gives the condition of the transformer. Trending of gases is very helpful in the analysis. DGA is one of the best ways to monitor the condition of the transformer and help the Owner plan repairs or replacements.

11 Infrared Thermography Scan Heat is the enemy for electrical equipment Heat breaks down electrical insulation 10 C Rule = ½ life Infrared thermography scanning Looks at thermal image of switchgear, busbars, connections, cables, etc. Hot spots and irregularities are discovered by trained technicians Problem areas can be corrected before they cause shutdowns or cause fires. Scanning Saves Equipment Technician scanning is much faster that tightening all bolts. Cannot see some circuit breaker problems without IR. Early detection and correction = preventative maintenance.

12 Infrared Thermography Scan F SP02 SP F 100 Spot 1 Temperature Spot 2 Temperature Spot 1 Rise over Spot 2 Ambient Temperature F 93.9 F F 68.0 F

13 Circuit Breaker Testing Contact Resistance Results vary with size and construction of circuit breaker less than 100 microhms for medium voltage Contact resistance exposes problems not detectable with IR when there is little load current. Insulation Resistance Phase to ground Phase to phase Functionality Tests Close, Open Trip Kirk key interlocks, etc.

14 Circuit Breaker Testing Cont d. Overcurrent Trip Point Calibration and Testing Secondary Injection Testing Electronic CB test sets for accurate testing Square D Cutler Hammer GE Siemens New Circuit Breakers with on-board secondary injection testing Cutler Hammer 1150 Trip Unit

15 Medium Voltage (> 600 Volts) Cable Testing New Cables Insulation resistance testing using hi pot at manufacturer s recommended values NETA use Table 10.6 of Acceptance Testing Specs. Leakage current should be <10 micro Amps for new cables. Existing Cables Watch out! Be careful what voltage you use on old cables. Conservative approach RMS X Square Root of 2 = Peak voltage Use peak value as DC value

16 Relay Testing Relays are typically used on medium voltage systems Older electro mechanical style relays (typical single phase) Newer models microprocessor based, 1 Phase + 3 Phase Incorporate metering and relay tripping. Programmable on site Fault analysis logging for retrieval Short Circuit and Coordination Studies At least 50% of facilities are not coordinated Poor maintenance Poor installation

17 Power Quality - Today s Perspective The quality of power 30 years ago was not much of an issue Linear Devices Today many devices disrupt and corrupt the quality of the power Utility Side Voltage Sags Impulses Transient Disturbances Loss of One Phase Over voltage

18 Power Quality Today s Perspective Customer Side Switch mode power supplies (non-linear device) Harmonic Distortion Overloaded neutrals Transformer heating SCR (non-linear device) Loose wiring Large motor starting

19 PQ Testing Power Quality Analyzer 3 phase microprocessor based analyzer that samples the voltage waveform 128 times per second. We set thresholds for voltages. By exceeding the thresholds, the machine is activated to record the events as they occur. Harmonic testing and analysis Measure voltage and current THD Analyze individual harmonic values Engineering investigation of problem and surrounding power distribution system by power quality engineer.

20 Main Switchboard Voltage Sag Model V RMS Sag Disturbance Three Phase Wye 340.0A Vc Ic 175.0V 170.0A 0.0V 0.00ns M SWBD 0.0A 5.83 ms/div ms 11/22/01 07:57:32.98 AM Channel Y1 Y2 Delta Voltage Channel Y1 Y2 Delta Current Time X1 X2 Delta

21 Main SWBD Voltage Sag on Phase C-N Model V Impulse Disturbance Three Phase Wye 640.0A Vc 0.0V 0.0A V 0.00ns M SWBD A 2.50 ms/div 50.00ms 11/22/01 07:57:32.98 AM

22 Main SWBD Utility Capacitor Switching Transient Phase B-N Model V Impulse Disturbance Three Phase Wye 2.1KA Vb 0.0V 0.0A V 0.00ns M SWBD -2.1KA 2.50 ms/div 50.00ms 12/03/01 09:48:07.93 AM

23 Time X1 X2 Delta Utility Capacitor Switching Transient Phase B-N Model V Impulse Disturbance Three Phase Wye 2.3KA Vb 0.0V 0.0A V 0.00ns M SWBD -2.3KA 2.50 ms/div 50.00ms 12/03/01 11:43:11.90 AM Channel Y1 Y2 Delta Voltage Channel Y1 Y2 Delta

24 Panel NEH1 Power Source Switching Transient Phase A-N Model V Impulse Disturbance Three Phase Wye 575.0A Va 0.0V 0.0A V 0.00ns Pnl NEH A 2.50 ms/div 50.00ms 01/03/02 02:00:54.74 PM

25 Panel NEH1 Power Source Switching Phase B-N Model V Impulse Disturbance Three Phase Wye 570.0A Vb 0.0V 0.0A V 0.00ns Pnl NEH A 2.50 ms/div 50.00ms 01/03/02 02:48:29.37 PM

26 Harmonic Distortion Voltage Waveform Model V Snapshot Waveform Three Phase Wye 50.0A Va 0.0V 0.0A V -50.0A 0.00ns ms PDU PnlD us/div 01/17/02 01:06:45.97 PM 1.0% 0.5% 0.0% 60Hz 2940Hz Distortion: thd=1.41% Odd=1.36%

27 Harmonic Distortion - Current Model V Snapshot Waveform Three Phase Wye 50.0A Ia 0.0V 0.0A V -50.0A 0.00ns ms PDU PnlD us/div 01/17/02 01:06:45.97 PM 32.0% 16.0% 0.0% 60Hz 2940Hz Distortion: thd=42.34% Odd=42.19%

28 How Do You Spot PQ Problems? Variable speed drives trip off line more than usual. Computer data errors that cannot be explained by hardware or software Lights flicker (not in a storm). Equipment power supplies have burned or damaged boards. Transformers overheating. Circuit breaker nuisance tripping. Motors overheating or failing easily. Voltages vary significantly from loose wiring. Computer screens wave or are disrupted.

29 Power Quality and Facility Maintenance Are Related Loose connections are one of the leading power quality problems Lack of coordination of overcurrent protection devices can cause blackouts that could have been avoided. Coordination Study Short Circuit Study Preventative Maintenance Infrared thermography scan looks for hot spots Transformer Testing Oil Quality Dissolved Gas Analysis Cable Testing Test Circuit Breakers Switchgear Maintenance

30 Conclusion Facilities today face tough problems: Harsh environments Power Quality Problems Need for 24/7 Reliability Compressed schedules A successful 21 st Century Facility needs four solid legs to stand on: Engineering Design Quality Installation Maintenance Testing

31 Conclusion Cont d. Excellent resources and standards from IEEE, NETA and NFPA for Testing and Maintenance A proper test is worth a thousand opinions. The right test equipment and experience will aid the Design Engineer in ensuring success for the Customer. Call IETC at for a quote today!