30 Colonnade Road North, Unit 300
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 MaxBIL 95KV Max / 1501KVA & Up
BIL 45KV Max / 1501KVA & Up
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.