Technical information
FAQ (Frequently Asked Questions)
Contact the manufacturer before tampering with your transformer. By obligation if it is still under guarantee, by caution if it is not.
- Gas discharge questions
- Overpressure questions
- Miscellaneous questions
Questions involving gas discharge
Question 1
Every time the transformer is switched on, the gas discharge contact moves to the fault position then returns to its normal position. No gas is seen in the body of the device (the large float is at the top of its tank).
Answer
Exceptionally, on certain types of transformers, the magnetic losses that occur when it is switched on (especially under little or no load) can be enough to actuate the reed of the DGPT2. This usually lasts no longer than 10 ms—one half cycle at 50 Hz—, which often makes the problem difficult to pinpoint.
Fitting the Anti-magnetic shield AC201 solves the problem entirely, and requires no special tools nor modifications to the DGPT2.
Question 2
When testing the DGPT2 and the associated servo systems, the gas discharge contact switches to its fault position and stays there. No gas is seen in the body of the device (the large float is at the top of its tank). Following this anomaly, the actuation of the contact is tested again using a magnet (see On-site testing). The contact does not change position anymore and remains closed in the fault position.
Answer
When testing, voltage or current surges may occur, most often caused by defective equipment, cabling, or relay errors. Long cables can also cause current surges in case of switching. Routing low voltage servo cables with power cables (motor power supply, transformer power, etc.) often leads to significant interference by electrical and electromagnetic induction. These various phenomena can cause the reed contacts to stick or be welded.
- Check the cabling, the servo systems, and the cable routing if necessary.
- If the contacts are simply stuck, testing the reed with a magnet will free them.
- If the contact is welded, the Reed contact PL513 must be changed, which is a quick and easy procedure. Upon request, we will ship a new reed with appropriate instructions.
Question 3
The gas discharge contact shows a fault. There is gas in the DGPT2’s body (the large float is at the bottom of its tank).
Answer
The device operated correctly, but it is important to determine whether the gas is decomposed dielectric fluid or ambient air.
- Inform the transformer’s manufacturer.
- Depending on the reply, sample the gas and/or dielectric fluid and have it analyzed.
- Send the results to the manufacturer and follow his directions.
If the gas is ambiant air, and if you are authorized to do so, you can purge the device to raise the fluid level in the device’s body. If the level does not rise (because of cold ambient temperature and low transformer load), the level can be raised without adding dielectric fluid by creating a slight negative pressure inside the DGPT2 using a bicycle pump with an inverted membrane or an adequate syringe.
Maneuvering the drain tap
The DGPT2’s drain tap can be used both for purging and for sampling.
- Remove the black plug and the locking pin.
- Mount the pump’s flexible outlet, syringe, or sampling device on the threaded part of the cock.
- Open the tap by turning the cock anti-clockwise.
- The cock must be screwed into the body of the tap. Sample or purge as required, then close the tap by turning the cock clockwise.
- Wipe the tap, fit the pin, and screw the black plug back on.
Questions involving pressure detection
Question 4
The tank overpressure contact shows a fault. This occurs frequently, as soon as the transformer reaches its operating temperature. The contact returns to normal when the transformer cools down.
Answer
There may be 2 causes to this problem :
- The transformer has a rigid tank and is not suitable for complete oil-filling, therefore the expansion of the dielectric fluid causes excessive pressure in the transformer’s tank. The transformer must not be used in these conditions, it must be modified before it is put back in service. Contact Automation 2000 or the transformer’s manufacturer, and refer to Choosing the right protection.
- Inadequate additions of dielectric fluid have been made, and the expansion of the dielectric fluid causes excessive pressure in the tank. In this case, remove the excess dielectric fluid, or contact the transformer’s manufacturer or Automation 2000.
Miscellaneous questions
Question 5
The body of the device has turned partly translucent or opaque. In addition, fine cracks can be seen on the surface of the Trogamid® body. There are no deposits which can hamper the transparency of the device’s body. Is the device UV resistant?
Answer
Trogamid® is impervious to UV. However, it is easily deteriorated by alcohols. Even an ambient atmosphere heavy with alcohol vapours will deteriorate Trogamid. The surface first turns opaque, then fine crackles appear which in turn lead to deeper cracks and finally to rupture, causing dielectric fluid leaks.
Note: Different types of alcohol cause different symptoms. For example, isopropyl alcohol causes crackling without first causing translucent or opaque spots to appear.
If the Trogamid is damaged, the only solution is unfortunately to change the device entirely. When cleaning deposits that may cause translucent or opaque spots, ensure that the product is entirely alcohol-free.