Howard HI-104 Single-Phase Pad Transformer - Manual (Page 21)

Document 2.4.96, Revision 0
March, 2013
21
Single-Phase Pad-Mounted Compartmental-Type Distribution Transformers
An optional arrester disconnector provides a means
to disconnect the fluid-immersed MOV arrester
ground for transformer testing without entering the
transformer tank. Two different styles of disconnec-
tors are available, one manufactured by ERMCO
Components Inc. (ECI) and one manufactured by
Cooper Power Systems (CPS). These two styles oper-
ate differently as indicated below.
Before testing the transformer, disconnect the ar-
rester using the following procedure.
1. Make sure the transformer tank is properly
grounded.
2. De-energize the transformer from a remote loca-
tion.
3. Ground all bushings and terminals.
4. Disconnect the MOV arrester by operating the
disconnector as described below.
For the CPS disconnector (identified by an
external black plastic cap):
a. Unscrew the black disconnector
cap from the shaft.
b. Re-attach the small diameter end
of the disconnector cap to the
shaft.
c. Push the handle and shaft toward
transformer until the shaft flange
is flush to the sealing gland.
For the ECI disconnector (identified by a
7/16” square brass metal head):
a. Unscrew the 7/16” square metal
head until the thread disengages.
b. Pull the shaft out to its full extent
(approximately 2”).
5. It is now safe to perform impulse, induced-poten-
tial or applied-potential tests.
After testing the transformer, reconnect the MOV ar-
rester using the following procedure.
1. Make sure the tank is properly grounded.
2. De-energize the transformer from a remote loca-
tion.
3. Ground all bushings and terminals.
4. Reconnect the MOV arrester by operating the
disconnector as described below.
For the CPS disconnector:
a. Pull the disconnector handle and shaft
fully away from transformer.
b. Unscrew the black disconnector cap
and re-attach it with the large diame-
ter end toward the transformer. Rotate
the cap clockwise to tighten.
c. Reinstall the black cap.
For the ECI disconnector:
a. Push the shaft inward until the
threads engage.
b. Tighten the 7/16” square head ac-
cording to the torque guidelines listed
in Table 4.
On double-door style transformers the arrester
disconnector may not be provided, and the fluid-
immersed MOV arrester must be manually discon-
nected before testing by opening the transformer
tank. Refer to “Opening the Transformer Tank” for
instructions.
The MOV arrester can be manually disconnected us-
ing the following procedure.
1. Make sure that tank is properly grounded.
2. De-energize the transformer from a remote loca-
tion.
3. Ground all bushings and terminals.
4. Relieve pressure inside the tank by operating the
pressure relief valve, being careful to avoid any
hot fluid that might be expelled from the valve.
5. Remove the tank cover.
6. Locate the disconnect point to which the arrester
line lead is attached.
7. Disconnect the arrester lead from its junction
point and isolate the lead end at least six inches
from any other part of the transformer.
8. It is now safe to perform impulse, induced-poten-
tial or applied-potential tests.
The following procedure should be followed to manu-
ally reconnect the arrester lead.
1. Reconnect the arrester lead to its junction point
using the hardware previously removed.
2. Re-install the tank cover.