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Q&A How could a damaged wire in split-phase power delivery create these voltages?

When the outage occurred, I observed the following The L1/G voltage difference was 120V (good). The G/L2 voltage difference was 90V (bad). The L1/L2 voltage difference was 30V (very bad!). If t...

posted 3y ago by Andy aka‭  ·  edited 3y ago by Andy aka‭

Answer
#2: Post edited by user avatar Andy aka‭ · 2020-08-03T17:28:09Z (over 3 years ago)
  • > When the outage occurred, I observed the following
  • - The L1/G voltage difference was 120V (good).
  • - The G/L2 voltage difference was 90V (bad).
  • - The L1/L2 voltage difference was 30V (very bad!).
  • If the L2 wire was broken then, due to capacitive coupling between L1 and L2 (and the use of a high impedance voltmeter), the voltage on L2 will appear to be close in value and phase angle to L1. Hence you see a 30 volt difference between L1 and L2 and L2 is circa 90 volts above ground.
  • Concusion: L2 is broken and naturally picks up a voltage die to capacitive coupling. I've seen this before.
  • > When the outage occurred, I observed the following
  • - The L1/G voltage difference was 120V (good).
  • - The G/L2 voltage difference was 90V (bad).
  • - The L1/L2 voltage difference was 30V (very bad!).
  • If the L2 wire was broken then, due to capacitive coupling between L1 and L2 (and the use of a high impedance voltmeter), the voltage on L2 will appear to be close in value to the L1 voltage. Hence you see a 30 volt difference between L1 and L2 and, L2 is circa 90 volts above ground.
  • Concusion: L2 is broken and naturally picks up a voltage due to capacitive coupling. I've seen this before.
#1: Initial revision by user avatar Andy aka‭ · 2020-08-03T17:25:49Z (over 3 years ago)
 > When the outage occurred, I observed the following
 - The L1/G voltage difference was 120V (good).
 - The G/L2 voltage difference was 90V (bad).
 - The L1/L2 voltage difference was 30V (very bad!).

If the L2 wire was broken then, due to capacitive coupling between L1 and L2 (and the use of a high impedance voltmeter), the voltage on L2 will appear to be close in value and phase angle to L1. Hence you see a 30 volt difference between L1 and L2 and L2 is circa 90 volts above ground.

Concusion: L2 is broken and naturally picks up a voltage die to capacitive coupling. I've seen this before.