Schneider Electric PowerLogic PM5300 Series Especificaciones descargar pdf (Pagina 58)

Power Meter 750 63230-507-201A1

Appendix C—Instrument Transformer Wiring: Troubleshooting Guide 03/2007

SECTION IV: 4-WIRE SYSTEM

TROUBLESHOOTING

Table C– 9: Section IV—Case A

Symptoms: 4-Wire Possible Causes

• kW = 1/3 of the expected value

• kVAR = 1/3 of the expected value

• power factor = 1/3 of the expected value

• All else is normal

• One CT polarity is backwards

NOTE: The only way this problem will usually be detected is by the Quick Check

procedure. It is very important to always calculate kW. In this case, it is the only symptom

and will go unnoticed unless the calculation is done or someone notices backwards CT on

a waveform capture.

Table C– 10:Section IV—Case B

Symptoms: 4-Wire Possible Causes

• kW = 1/3 of the expected value

• kVAR = 1/3 of the expected value

• 2 of the 3 line-to-line voltages are low

• power factor = 1/3 of the expected value

• All else is normal

• One PT polarity is backwards

NOTE: The line-to-line voltage reading that does not reference the PT with backwards

polarity will be the only correct reading.

Example: , ,

In this case, the A-phase PT polarity is backwards. is correct because it does not

reference .

277= V

= V

277=

Table C– 11:Section IV—Case C

Symptoms: 4-Wire Possible Causes

• One line-to-neutral voltage is zero

• 2 of the 3 line-to-line voltages are low

• kW = 2/3 of the expected value

• kVAR = 2/3 of the expected value

• kVA = 2/3 of the expected value

• Power factor may look abnormal

• PT metering input missing (blown fuse, open phase disconnect, etc.) on the

phase that reads zero.

NOTE: The line-to-line voltage reading that does not reference the missing PT input will be

the only correct reading.

Example: , ,

In this case, the B-phase PT input is missing. is correct because it does not

reference .

277(

)

= V

480=

Table C– 12:Section IV—Case D

Symptoms: 4-Wire Possible Causes

• 3-phase kW = 2/3 of the expected value

• 3-phase kVAR = 2/3 of the expected value

• 3-phase kVA = 2/3 of the expected value

• One phase current reads 0

• All else is normal

• The CT on the phase that reads 0 is short-circuited

• Less than 2% current (based on CT ratio) flowing through the CT on the

phase that reads 0

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Schneider Electric PowerLogic PM5300 Series Especificaciones Pagina 58

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