Maintenance (continued) – Howard SVR1 Regulator User Manual

Page 15

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SVR-1 Step Voltage Regulator

Document No. 2.4.114

Revision: 03

Issued: March, 2012


Copyright © 2012 Howard Industries, Inc.

before beginning untanking procedures.

Remove the control cable from the terminal block

enclosure and, if necessary, the control box from

the tank.

Loosen the cover band and remove it from the


The regulator can now be removed from the main

tank using the cover lifting eyes (Figure 11).

2. Check to verify all hardware and connections are


3. Check the condition of wire insulation, looking for any

cracks or other deterioration.

4. Inspect the tap changer’s arcing contacts to verify

operational condition. Since numerous factors affect

a contact’s wear rate, no single criteria can be used

to predict a contact’s remaining life and the need to

replace it. Refer to “Maintenance Instructions, TC-1

and TC-2 Load Tap Changer” (Document 2.4.58) and

follow the recommended procedure for inspection

and maintenance of the load tap changer switch


5. Reinstall the regulator’s internal assembly using the

reverse procedure. After the inspection is completed,

the regulator can be safely returned to service

according to the procedure discussed on pages 10

and 11.

This procedure applies if the oil level in the regulator has

been lowered to a level that exposes part or all of the

coils to air or the internal assembly has been removed

from the tank.

1. Every container or tote of transformer oil used in

the filling process should be visually inspected and

tested for water or other possible contaminants

before proceeding with the filling process.

2. If the coils are out of oil for more than four hours,

the coils must be baked for at least 24 hours at a

temperature of 100°C (212°F) prior to re-tanking

the internal assembly. The tap changer must not be

exposed to a temperature above 110°C (230°F).

The unit should not be re-baked more than two


3. Connect the vacuum pump suction line to the

pressure-vacuum fitting near the top of the tank.



4. Connect the oil fill line to the tank at the bottom drain

valve connection.

5. Start the vacuum pump.
6. When the vacuum level inside the tank reaches 2000

microns (2 Torr) start timing. When this vacuum level

has been maintained for a minimum of 1 hour the oil-

filling may be started.

7. Continue to fill the unit until the oil level fills the sight

glass (25°C oil level).

8. After the oil filling has been completed, continue to

hold the vacuum level for 1 additional hour.

9. If vacuum oil filling is not possible, the re-tanked

internal assembly should be allowed to soak in oil for

at least five days before energizing.


Cooling fans (when present) have sealed bearings and do
not require maintenance.