© 2020 ASCO Power Technologies. All Rights Reserved
For troubleshooting, call technical assistance at 1-800-237-4567 or [email protected]
10
IO-70064
05/2020
ASCO 460/465/480/485 Surge Protective Device (SPD)
Grounding
Delta and
Resistance-Grounded
Power Systems
HAZARD OF ELECTRIC SHOCK, EXPLOSION, OR ARC FLASH
• Ungrounded power systems are inherently unstable and can produce
excessively high line-to-ground voltages during certain fault conditions.
During these fault conditions any electrical equipment, including an
SPD, may be subjected to voltages which exceed their designed rat-
ings. This information is being provided to the user so that an informed
decision can be made before installing any electrical equipment on an
ungrounded power system.
• Resistance-grounded power systems must be maintained in an over-
damped state to limit voltage overshoot and duration during operation.
•
Verification and adjustment of correct power system damping should be done:
– Periodically as part of normal system maintenance.
–
Following power system modifications.
Failure to follow these instructions will result in death or serious injury.
The ASCO 460/465/480/485 product is intended for use on resistance-
grounded power systems where the power system has been set for, and
is maintained in, an over-damped state. For the power system to be over-
damped, the current through the grounding resistor during a bolted phase-
to-ground fault must be significantly greater than the total charging current of
the system.
Periodic engineering evaluation of the power system is required to determine
the worst-case charging current of the system and to adjust the grounding
resistance accordingly. As the power system is modified, the value of the
grounding resistor must be evaluated and adjusted to maintain the system in
the over-damped state.
DANGER
