High neutral-to-ground voltage

This signature is a voltage between the neutral conductor and ground that is higher than it should be on the AC side of the system. Some surge protective devices have built-in neutral-to-ground voltage indicators: when they sense excessive voltage, the red service LED blinks and the audible alarm cycles. Inside such a device, a differential voltage circuit watches the neutral-to-ground voltage. A sustained excess slowly overheats a resistor until its heat-shrink sleeve shrinks, but brief transient spikes do not cause this. A common cause is a missing XO or neutral-to-ground bonding jumper, which leaves the system ungrounded and can lead to abnormally high line-to-ground voltages. This is an installation error. It needs immediate attention, because the surge protective device keeps reacting to the overvoltage until it fails. During an inverter inspection, measure neutral-to-ground voltage together with line-to-line, line-to-neutral and line-to-ground voltage while the AC is on, but only if it is safe to do so. Before working on the AC terminals, use a voltage detector to confirm there is no voltage from neutral to ground, phase to ground and phase to neutral.

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• sentence 1: support check: partial - Passages say excessive N-G voltage is detected, but not that it is on the AC side or defined as a signature; "higher than it should be" is a loose paraphrase of "excessive".
• sentence 3: support check: partial - Differential circuit, resistor overheating, shrink wrap, and no effect from transients are stated, but "sustained" and "slowly" are only implied by "eventually".
• sentence 7: support check: partial - The passages say to check absence of voltage with a voltage detector on the AC terminal blocks between those pairs, but do not say "before working on" them.
• sentence 1: review: partial - The passage describes excessive N-G voltage detected by the SPD, but it does not say this is on the AC side of the system.
• sentence 4: review: partial - A missing XO/N-G bonding jumper leaving the system ungrounded and leading to abnormally high L-G voltages is stated, but the passage never calls it a 'common' cause.
• sentence 7: review: partial - The voltage-detector absence test between phase-ground, neutral-ground and phase-neutral on the AC terminals is stated, but 'before working on the AC terminals' is framing the passage does not give. -->