voltage-limiting effectiveness of the ESA. Fusing
of the ESA is not recommended because protection may
be lost without the operator's knowledge. If fusing
is necessary, a light to indicate a blown fuse will
be provided on the ESA enclosures.
**************************************************************************
The ESAs shall be located so that leads of minimum length connect the ESA
ground terminal to the enclosure. The total lead length connecting the ESA
to the filter and the ESA ground terminal to the enclosure shall be less
than 300 mm 12 in. Power line ESA wiring shall be No. 4 AWG minimum.
Communication/signal line ESA wiring shall be of the same or heavier gauge
than the communication/signal line conductor.
2.7.1.3
Voltage Characteristics
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NOTE: Clamping voltage requirement is intended to
ensure that the ESA does not have excessive series
resistance. The specific value should be chosen
after reviewing manufacturer's data.
Specified dc breakdown voltage (or MOV voltage at 1
milliampere dc current) for dc and single phase ac
power should be in the range of 150 to 200 percent
of the peak (not rms) operating voltage. Use 200 to
250 percent on three-phase circuits, so that a
short-circuit fault in one phase will not fire ESA
on the other two phases.
The spark gap dc breakdown voltage requirement is
intended to ensure that the spark gap is a
low-inductance, fast device. The precise values are
not critical and should be chosen after reviewing
ESA catalog information.
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Measurements of (MOV) voltage at 1 mA dc current and spark gap dc breakdown
voltage shall be made in accordance with the following procedure. Testing
shall be performed with the ESAs mounted in the filter/ESA assembly
enclosure or mounted on a metal plate by the same holding method which will
be used for mounting in the enclosure. A variable dc power supply shall be
connected between the ESA terminal and the enclosure (or plate). The
applied dc voltage shall be increased at a rate not to exceed 10 percent of
the rated firing voltage per second. The (MOV) voltage at 1 mA dc current
is the power supply output voltage, when the output current is 1
milliampere. The spark gap dc breakdown voltage is the applied voltage
just prior to breakdown (indicated by a rapid decrease in the voltage
across the device).
The power supply shall be de-energize immediately
after the value has been recorded. MOV direct current breakdown voltage at
1 milliampere dc current shall be at least [340] [500] [1,000] [_____]
volts and less than [425] [1,500] [_____] volts. MOV testing shall be in
accordance with IEEE C62.33. Spark gap direct current breakdown
(sparkover) voltage shall be at least [500] [1,000] [_____] volts and less
than [1,500] [3,000] [_____] volts. Spark gap impulse sparkover voltage of
the ESA shall be less than 4,000 volts. This voltage shall be on surges of
either polarity having a rate of rise of 1,000 volts/nanosecond. Testing
of the ESA impulse sparkover voltage shall be performed with the spark gaps
mounted in the filter/ESA assembly enclosure or mounted on a metal plate by
SECTION 13095A
Page 39
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