CEDASPE EB / ET / RR / GQ — gas relays to EN, UNEL and AS standards

Description

CEDASPE Buchholz relays are installed in the pipe between the tank of an oil power transformer and the conservator. They respond to gas released during internal faults, to loss of oil and to a sudden oil surge towards the conservator. The range covers several models for different national standards. The EB is made to EN 50216-2, the ET and RR to the Italian UNEL, the GQ to the Australian AS standard. The RR and GQ series were previously produced under the ETI brand. The relays are interchangeable with devices of other manufacturers by DIN/EN, UNEL and AS mounting dimensions, so replacement on an operating transformer means swapping the relay without modifying the pipework.

The relays are produced for nominal bores of 25, 50, 75/80 and 100 mm. The oil flow velocity at which the flap operates lies within 0.65–2 m/s. The number of contacts is from 1 to 4, and up to 6 in the RR. For the EB the standard schemes are as follows. Type A has 2 normally open contacts, one for alarm and one for trip, type L has 2 changeover contacts, type G 3 normally open contacts, of which 2 are for trip. For relays with a 50 and 80 mm bore there are special schemes S2, S3, S4 with different combinations of changeover and normally open contacts, as well as type R, in which the trip contact latches after an oil surge and is reset manually by a button on the cover.

Rated current of the normally open contact is 2 A, of the changeover contact 1 A, short-time current 10 A for 30 ms. The relay cover carries a gas release cock, a button for testing the electrical circuits, a valve for pneumatic testing and a terminal box cast integrally with the cover with two cable glands. Cast parts are coated with epoxy primer and polyurethane paint with a total thickness of 80 µm in RAL 7030, screws and washers are stainless steel. Degree of protection of the terminal box is IP65 to EN 60529, up to IP67 on request. The coating is designed for outdoor installation in tropical climates and under industrial pollution, and corrosion resistance has been tested in a salt spray chamber to ASTM B 117 for 200 h.

Mechanical requirements are also specific. The relay must not operate falsely under sinusoidal vibration of class 4M4 to EN 60721-3-4 and under a vertical shock of 100 m/s2. Continuous internal pressure is 50 kPa, the relay withstands an overpressure of 250 kPa for 2 min and a vacuum of 2.5 kPa for 24 h, so it does not have to be removed during vacuum treatment of the transformer. Operating oil viscosity is from 1 to 1100 mm2/s, minimum oil temperature -40 °C.

The operating instructions describe the design of the EB and ET models, contact signals, inspection and maintenance, draining of the insulating liquid, disposal and drawings of all sizes. During scheduled inspections, the presence of gas is checked through the inspection window, gas is released through the cock and, if necessary, a sample is taken for analysis, and the button and pneumatic valve are used to check operation of the floats and alarm circuits.

Technical specifications

Customs codes

Codes are for reference: the final code is determined at declaration for the specific model.

Questions and answers