7
PowlVac
®
Electrically-Operated Ground and Test Device
IB-65060
III. EQUIPMENT DESCRIPTION
A. GENERAL DESCRIPTION
The PowlVac
®
Electrically Operated Ground and Test
Device (see Figures 1 and 2) is a drawout element
that can be inserted into the circuit breaker compart-
ment in the same manner as a Powl-Vac
®
circuit
breaker.
The PowlVac
®
PV 38 Electrically Operated Ground
and Test Device provides a means for obtaining
access to the primary disconnect devices of the
switchgear cell for purposes of grounding the primary
circuits or conducting certain high voltage test
procedures such as conducting high voltage with-
stand (hipot) tests.
The grounding switch is operated by a stored energy
mechanism. It is capable of applying the ground
against a LIVE circuit if operational errors have not
cleared the circuit. However, in such a case, the
relaying at the source of power is expected to cause
the source interrupter to clear the circuit.
B. POWER GROUNDING SWITCH OPERATION
1) Closing
The power grounding switch is closed by the remote
operating station at the end of a 50 ft. long cable that
is supplied with the device (Figure 9). Upon depress-
ing the CLOSE push-button (note that the push-
button does not have to be held depressed):
1.
The closing springs start to charge.
2.
After the springs are fully charged, the springs
automatically discharge to close the switch
contacts.
Once the ground switch is closed, it can be locked
into the CLOSED position by removing the cable
from the receptacle on the device.
2) Opening
The grounding switch can be opened electrically
using the remote operating station. The OPEN push-
button must be depressed. For safety reasons, the
switch is prevented from opening in less that 20
seconds after closing.
C. KEY LOCKS
1) Key Lock K1 (Keys KU and KB)
The key lock K1 interlock is a two cylinder lock used
to electrically enable or disable the ground and test
device.
Key lock K1 interlock is a two cylinder transfer lock
equipped with an electrical switch element. The
switch is closed when key KB is retained. When the
switch is open, the ground and test device is electri-
cally disabled and key KU is retained (see Figure 1, u
and Figure 3).
NOTE: When multiple electrical ground and test
devices are supplied for an installation, the customer
feeder ground and test devices are normally supplied
with similar interlock functions as that of the Con
Edison specification. In these cases, key KU is not
present, but is instead supplied with a key KCF (Key,
Customer Feeder) for Con Edison customer use.
Key KU and key KCF are non-interchangeable.
2) Key Lock K2 (Keys KB and KC)
Key lock K2 interlock is a two cylinder lock used to
mechanically lock the ground and test device in the
OPEN position (see Figure 1, k and Figure 4).
14. Check for dielectric integrity at 60kVAC across
the terminals to ground with the grounding switch
OPEN.
C. X-RAYS
When high voltage is applied across the contacts of a
vacuum interrupter, there is the possibility of the
generation of X-rays. The intensity of this radiation is
dependent on the amount of the peak voltage and the
distance of the contact gap. Radiation levels are
negligible at the normal operating voltage for this
type of equipment. At the voltages specified for
testing, personnel must be located in front of the
electrical ground and test device such that the two
layers of steel used in the frame and front cover
construction are between personnel and the vacuum
interrupters. Personnel must be located no less than
one meter from the front of the electrical ground and
test device. THE ELECTRICAL GROUND AND
TEST DEVICE SHALL BE EITHER FULLY OPEN
OR FULLY CLOSED DURING HIGH POTENTIAL
TESTING. TEST SHALL NOT BE CONDUCTED
WITH THE CONTACTS PARTIALLY OPEN.
