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Ottawa, Ontario, Canada, K2E 7J6
Tel: 866-300-1527 Fax: 613-224-6012
INSTALLATION AND MAINTENANCE
MANUAL
POWER SYSTEMS TECHNOLOGY
DRY-TYPE MINISUB WITH NGR
Rev. 1 2015
CONTENTS
INSTALLATION AND MAINTENANCE GUIDE
1. GENERAL
2. INSPECTION UPON RECEIPT
3. HANDLING
4. STORAGE
4.1 Drying Core & Coil Assembly
4.1.1 Internal Heat Method
4.1.2 External Heat Method
4.1.3 External & Internal Heat Method
4.2 Determining Dryness Level
5. TESTING
5.1 General
5.2 Tests
6. INSTALLATION
6.1 Sprinkled Area
6.2 Bolted Joints
6.3 Sound Level
6.4 Grounding
6.5 Top Cable Entry
7. BEFORE ENERGIZATION
8. REMOVING FROM SERVICE
9. OPERATION
10. MAINTENANCE
10.1 Inspection
10.2 Cleaning
11. WARRANTY
1.
GENERAL:
DANGER
There is a hazard of electric shock or burn whenever working in or around electrical
equipment. Power must be locked off before working inside a transformer enclosure.
This equipment is to be installed and maintained by qualified personnel only.
The successful and safe operation of dry type transformers is dependent upon proper handling,
installation, and maintenance. Neglecting certain fundamental installation and maintenance
requirements may lead to personnel injury and the premature failure of the transformers as well
as damage to other property.
2.
INSPECTION UPON RECEIPT:
Immediately upon receipt of the shipment, identify all units and check them against the shipping
list. Make a visual examination to detect any damage which may have been incurred during
transit. This examination should be external and internal. If any damage is discovered, file a
claim immediately with the carrier and send notice of the extent of damage to the local sales
office, giving complete identification, carrier’s name and railroad car number if shipment was
made by rail. The information will enable the company to supply necessary data in support of
claim.
3.
HANDLING:
Unless special arrangements have been made with the customer, all transformers are shipped
with the core and coil assembly attached to the external enclosure. This is to facilitate lifting
and handling, and to provide protection during shipment. All transformers may be dragged or
skidded into position. Core and coil units are shipped on skids and should be left on the skid for
handling because, unless special arrangements have been made, the base structure is not
designed for skidding or rolling. Lifting eyes are located on the top frame of the core & coil
assemblies. The eyes are designed to allow overhead lifts with a crane. Care should be taken
when lifting to prevent cables or slings from damaging enclosures or other parts of the
transformer. (See FIG. 1)
CAUTION - Never attempt to lift a transformer from points other than the lifting
eyes provided. No transformer should be laid on its side or end for any reason. The
windings, structure and vibration isolators are designed to handle the normal weight and
stress from shipment and usage. These parts are not designed to accept stresses from
tipping or similar actions. Damage beyond repair can occur if transformer is turned on
its side or end.
4.
STORAGE:
Any transformer which is not installed and energized immediately should be stored in a dry
clean space having a uniform temperature to prevent condensation. Preferably, it should be
stored in a heated building having adequate air circulation and protected from cement, plaster,
paint, dirt, and water. In locations where moisture and condensation can exist, it is
recommended that heat lamps or space heaters be installed. Areas which can flood or retain
water should be avoided. The protective plastic wrapping should be left in place during storage.
This provides protection from moisture and falling dirt. If the transformer has been exposed to
moisture either before installation or after an extended shutdown period then see the following
instructions.
4.1 Drying Core and Coil Assembly:
There are three methods that may be used to dry the core and coil assembly
1) Internal heat
2) External heat
3) External and internal heat
Before any of the above methods are used any free moisture should be blown or wiped off the
windings in order to reduce drying time. Note; The pressure of compressed air used should not
exceed 25PSI and the air must come from a dry source.
4.1.1 Internal Heat Method
For this method, a source of impedance voltage is required. The transformer should be located
in a well ventilated dry area and one winding should be short-circuited. Voltage at normal
frequency should then be applied to the other winding to circulate 50 – 75 % of normal current.
Generally, the voltage required will be the rated voltage times the per unit impedance. The
winding temperature should not be allowed to exceed the average winding temperature rise or
100 Deg. C. whichever is greater. If the transformer is fitted with a winding temperature
thermometer then this can be used to measure the temperature, or as an alternative an IR
Thermometer can be used. Note: If an IR device is used then the temperature measured at the
coils should be limited to 100° C.
4.1.2 External Heat Method
External heat may be applied by one of the following methods
1) By placing the core and coil assembly in a suitably ventilated oven
2) By directing heated air up through the winding ducts.
Since it is extremely rare that a suitable oven would be available at the average site where a
transformer would be located the usual drying method would be No. 2. This method can be
achieved by the means of suitably rated stripheaters located inside the enclosure under the
coils, or by utilizing heaters with fans blowing hot air into the transformer. Note: To be most
effective the air should be directed to flow up into the winding ducts of the core and coil
assembly
4.1.3 External and Internal Heat Method
This method involves using both of the two methods as specified above at the same time and
would be the quickest way to dry the core and coil assembly.
4.2 Determining Dryness Level
The dryness level can be determined by taking insulation resistance readings at intervals
during the drying process. The first reading would be taken before the drying process starts to
obtain a base reading, then readings would be taken at 2-hour intervals until the unit is deemed
dry. The following table gives minimum resistance values which must be reached before the
transformer is put into service.
MINIMUM INSULATION RESISTANCE TABLE
Test Between
1500KVA Max
1501KVA & Up
1501KVA & Up
BIL 95KV Max
BIL 45KV Max
BIL 60KV & Higher
Core – Ground
Not Insulated
Not Insulated
50 Meg Ohms
LV - Ground
100 Meg Ohms
100 Meg Ohms
100 Meg Ohms
HV - Ground
100 Meg Ohms
100 Meg Ohms
100 Meg Ohms
LV - HV
100 Meg Ohms
100 Meg Ohms
100 Meg Ohms
Fully dried transformers can be expected to have readings 5 to 10 times these minimum values.
5.
TESTING
5.1 General
Preservice tests should be carried out after installation and before a new or repaired
transformer is put into service. Also, periodic tests should be carried out as a preventative
maintenance procedure.
If a transformer is known to be wet or has been subject to damp conditions then it should be
dried out before testing, See 4.1 for drying procedures
5.2 Tests
The following tests should be carried out and the results kept for future comparison
1) Insulation resistance test
2) Applied voltage test (Hi-Pot test)
3) Ratio test
Applied Voltage Test: The initial installation test should be limited to 75% of the factory
test value, and subsequent routine maintenance test should be limited to 65% of the
factory test value.
6.
INSTALLATION:
Dry type transformers are for indoor use unless the enclosure is specifically designed for
outdoor weather-proof service. They are cooled by means of free circulation of air, the
maximum ambient temperature of which should not exceed 40 ‘C. Damage may result if the air
flow is restricted, or the transformer is loaded beyond its rated capacity. Due to various building
and room constructions, it is recommended that applicable codes be followed. Factors which
should be kept in mind when locating Dry-Type Transformers are: Personnel safety,
accessibility, ventilation, locations affecting sound level, and environmental conditions.
Installations should be made in an area reasonably free from dust, moisture chemical and
corrosive vapours or fumes. Dry-Type Transformers must be installed in an upright position.
If the Transformer Enclosure has an open bottom:- DO NOT INSTALL ON OR OVER
COMBUSTIBLE SURFACES.
6.1 Installation in Sprinklered Area:
WARNING:- ADDITIONAL MEANS COULD BE REQUIRED AT TIME OF
INSTALLATION IN ACCORDANCE WITH THE CANADIAN ELECTRICAL CODE, PART 1 ON
SPRINKLERED EQUIPMENT TO DIRECT WATER SPRAY WHEN SPRINKLER HEADS ARE
WALL MOUNTED IN CLOSE PROXIMITY TO THE TRANSFORMER SO THAT THE ANGLE
BETWEEN THE SPRINKLER HEADS AND OPENINGS IN THE ENCLOSURE IS GREATER
THAN 45° FROM THE VERTICAL.
6.2 Bolted Joints:
All joints suitable for field connection of cable or bus have tin-plated contact surfaces. The lug
or bus used for connection should be tin-plated, or silver-plated. When plated parts are joined,
no surface preparation other than ensuring clean surfaces is required. Simply bolt the parts
together with the hardware supplied.
Some tap connections and other joints involve bare aluminum or copper. If it is necessary to
change taps or assemble a joint of bare aluminum or copper, lightly clean the contact surfaces.
Once the contact areas have been abraded, assemble the parts and tighten securely. Always
use two wrenches when breaking or making joints to prevent damage to parts.
CAUTION - Make only those connections shown on the nameplate or connection
diagram. Before energizing, check all jumpers for proper locations, and all bolted connection for
tightness.
To ensure good electrical connections, the following torque values must be adhered to:
1/4-20 Bolt - 10 Foot pounds
3/8-16 Bolt - 20 Foot pounds
1/2-13 Bolt - 40 Foot pounds
Cast Coil Tap Connections - 12 to 15 Foot pounds Max.
6.3 Sound Levels:
If noise is a factor in the location and operation of any transformer, special consideration should
be given to the installation of the equipment. Many locations can result in an amplification of the
sound level. If a unit is installed in a quiet hallway, you may notice a definite hum. If the unit is
installed in a location it shares with other equipment such as motors, pumps, or compressors,
the transformer hum will probably be unnoticed. The transformer is designed to produce a
minimum sound level when the following directions are followed:
A. Connections to primary and secondary terminals made with flexible connectors.
B. All transit bolts and shipping braces should be removed so unit will float on rubber
isolation pads. (See FIG. 2)
C. All enclosure hardware tightened so panels do not vibrate.
Note:
The isolation pads shipped with open units should be installed under the unit mounting plates
or channels. (See FIG. 3)
6.4 Grounding:
All core and coil structures have a flexible ground connection to the enclosure which ensures
that all dead metal parts have the same potential. The transformer enclosure should be solidly
grounded so that no danger will exist for operating or maintenance personnel. A transformer
ground stud or ground bus is provided for the customer’s ground connections. The grounding
conductor for the transformer should have a current-carrying capacity in accordance with the
National Electrical Code.
6.5 Top Cable Entry:
Top cable entry is not permitted in the main transformer compartment in accordance with CSA
C22.2 No.47-13. If the enclosure is fitted with air terminal chambers barriered off from the main
compartment, then cables may be brought into the top of these terminal chambers.
CAUTION - Installation should be performed only by experienced and qualified
personnel. No attempt should ever be made to change the taps, or make cable connections
while the transformer is energized. To maintain safe operating conditions, do not remove the
panels or cover while the transformer is in operation.
7.
BEFORE ENERGIZATION:
Before energizing the transformer, loosen or remove all shipping hardware, and store for future
use.
Transformers are provided with vibration isolators for installation under the core and coil
assembly. If these isolators are supplied loose then they must be installed before energizing
the unit. A location diagram is supplied with the transformer.
Check all tap jumpers for proper locations, and all bolted connections for tightness.
8.
REMOVING FROM SERVICE:
If the unit is to be moved, it will be necessary to replace the core & coil transit bolts and any
shipping braces that might protect the assembly during movement.
9.
OPERATION:
To maintain safe operating conditions do not remove panels or covers over openings in the
enclosure while the transformer is energized.
CAUTION - Never attempt to change taps or connections unless the transformer
is de-energized and all windings are grounded.
For all relatively clean and dry indoor installations, the transformer will operate satisfactorily
under normal conditions of energization and load. There is no concern over the transformer’s
ability to retain its electrical strength during reasonable periods of shut down. Under severe
conditions and extended shutdown periods condensation may form and ultimately be absorbed
into the insulation if such a situation occurs, the transformer should be inspected for visible
signs of moisture before re-energized. The transformer should be dried. See 4.1 for drying
procedures.
Transformers should not be overloaded for a long period of time. The resulting temperature can
cause insulation deterioration and transformer failure. Transformers 300 Kva and above (Class
ANN) are suitable for the addition of fan cooling equipment (Class ANN/ANF) which will permit
load increases of 33% over the self-cooled nameplate rating without exceeding temperature
ratings. Only forced-air equipment recommended or supplied by the factory should be installed.
It is recommended that caution be exercised when operating in the forced-air rating. While
temperature will not be exceeded, provided all fans are kept operational, the loss of a fan motor
can allow damaging temperatures. The ANN/ANF rating is intended to supply additional
capacity for emergency and peak loading rather than capacity for a normal operating condition.
EXTERNAL FANS, i.e.: fans blowing on the outside of the enclosure or louvres must not be
added to the unit. This practice can result in misdirected air flow which can retard or stop
normal convection through cooling ducts, and can result in over-heating.
10.
MAINTENANCE:
10.1 Inspection
Inspection should be made at regular intervals and corrective measures taken when necessary
to assure the most satisfactory service. The frequency at which the transformer should be
inspected depends on operating conditions: i.e.: For clean, dry locations, an inspection annually
may be sufficient, for other locations, such as contaminated with dust or chemical fumes
monthly inspections may be required.
Points for inspection:
a)- Dirt, especially accumulations on insulating surfaces or areas which would tend to restrict air
flow.
b)- Loose or corroded connections.
c)- Signs of overheating and of voltage creepage over insulating surfaces as evidenced by
tracking or carbonisation.
d)- Evidence of rusting, or corrosion of the paint should be corrected.
e)- If the enclosure is fitted with louvres and filters, then the filters should be inspected and
cleaned if necessary. See sketch on following page for filter removal instructions. As a general
rule the filters should be inspected annually when the unit is installed in a normal environment.
However, if the unit is in an extremely dusty or dirty area, then the filters should be inspected and
cleaned more frequently to ensure proper air flow. This frequency of inspection in such areas can
only be determined by a trial and error method. e.g. Start a monthly inspection regimen, and if it is
found that this is too often, extend the time between inspections until an optimum frequency is
established.
Inspect the resistor periodically as follows:
1) De-energize the system being grounded and disconnect the resistor’s neutral.
2) Remove the required covers to allow for visual inspection of the resistor’s internal
components.
3) Ensure that all connections and fasteners are tight, that no insulators are cracked and that
there are no signs of damage from heat, vibration, etc.
4) Use an Ohmmeter to verify the unit’s resistance and the continuity of all connections.
Resistance should be +/- 10% of the nominal value (see nameplate).
5) Use a Megger or Hi-pot to verify the insulation.
6) Clean the unit for excessive dust. If water is used for cleaning make sure the unit is perfectly
dry before reconnecting.
10.2 Cleaning:
If excessive accumulations of dirt are found on the transformer windings or insulators, the dirt
should be removed to permit free air circulation and to guard against the possibility of insulation
breakdowns. The windings may be cleaned with a vacuum cleaner, or with dry compressed air.
The use of a vacuum cleaner is preferred as the first step in cleaning, followed by the use of
compressed dry air or nitrogen. (25PSI Max.)
11.
WARRANTY
We warranty our products to be free from defects in material and factory workmanship. When
the product described herein is installed and used according to our instructions, the original
purchaser from us has the following warranty.
If any product of ours is found by us to be defective or not to be as ordered, and a written claim
is made to us, we will repair or replace the said product or issue credit for the same at our
option, to the original purchaser, C.I.F. factory.
This warranty terminates on the earliest of twelve months from date of installation or eighteen
months from date of shipment from our plant. There is no other representation, warranty or
condition in any respect, expressed or implied, statutory or otherwise, in contract, tort,
otherwise, other than the above, nor will we be liable in any way for consequential damages,
however caused, including damages arising out of our own negligence or that of our servants,
staff, agents or representatives.
We expressly disclaim any responsibility for expenses incurred in removing the said defective
product or installing or using any replacement product or for loss of time or use of the said
defective product, transportation costs, or any other indirect, incidental or consequential
damage or inconvenience.
This warranty does not apply if our product has been damaged due to improper installation,
alteration, abuse or misuse, accident, fire, flood or Act of God.