General Specifications

BUCHHOLZ RELAY

General specifications

The gas and oil actuated (Buchholz) relay is designed to detect faults as well to minimiz the propagation of any damage which might occur within oil-filled transformers, capacitors and reactors supplied with oil conservator. The relay is therefore particularly effective in case of:

•Short-circuited core laminations •Overheating of some part of the •Earth faults •Broken-down core bolt insulation windings •Puncture of bushing insulators •Bad contacts •Short-circuits between phases inside tank.

Furthermore the relay can prevent the development of conditions leading to a fault in the transformer, such as the falling of the oil level owing to leaks, or the ingress of air as a result of defects in the oil circulating system. Construction

CASING : non porous weatherproof compact casting INSULATION : 2000V 50Hz between terminals and of light aluminium alloy painted. earth for a 60 secs. time COVER : non porous weatherproof compact casting WORKING TEMPERATURE : oil temperature of light aluminium alloy painted. On the cover are range:-25/+100°C. located: the terminal box, the valve of pneumatic test, VIBRATION TEST (in normal operative the breather cock, the button for mechanical test of conditions) : alarm and trip circuits. • oscillation amplitude: 2mm INSPECTION WINDOWS : special tempered glass • time diagram: 0Hz100Hz 30 sec. with graduated scale in cm3. 100Hz (200 vibrations/sec.) 60 sec. 100Hz 0Hz. 30 sec. CONTACTS : they can be mercury switches or CONTACTS CAPACITY TO WITHSTAND magnetic actuated switches (reed contacts). On request VIBRATIONS : it’s possible to supply change-over switches. Mercury sw.:150 horizontal vibrations/sec. (75Hz) SWITCHES CHARACTERISTICS : first signals of closing contacts • rated voltage: 24250V AC or DC 120 vertical vibrations/sec. (75Hz) • rated current: 0,5A (10000 tests) first signals of closing contacts • breaking capacity: 2A AC (cos=0,425% - 50Hz) R eed sw. : 200 horizontal vibrations/sec. (100Hz) 2A DC (T=L/R=40msec). no one signal of closing contacts 200 vertical vibrations/sec. (100Hz) MECHANICAL PROTECTION DEGREE: IP 54 no one signal of closing contacts .

OPERATION

SLIGHT FAULTS : when a slight fault occurs in the housing, thus causing its oil level to fall. As a result, transformer, the small bubbles of gas, which pass the upper float rotates on its hinge and operates the upwards to the conservator, are trapped in the relay alarm switch, thus operating an external alarm device. SERIOUS FAULTS : when a serious fault occurs in The tripping device is regulated in such a way that in the transformer, the gas generation is violent and transformers having forced oil cooling, the surges causes the oil to rush through the connecting pipe to resulting from the starting of the oil circulating pump the conservator. will not cause mal-operation of the relay. In the relay this oil surge impinges on the flap fitted on An oil leak in the transformer causes the oil level in the the lower float (located in front of the hole for the oil relay to fall, thus operating first the alarm (upper) float passage) and causes the rotation of the float itself, thus and then the tripping (lower) float. operating the tripping switch and disconnecting the The ingress of air into the transformer, arising from transformer. The float remains in the trip position even defects in the oil circulating system or from other if the oil flow comes to a stop (the reset is done by causes, operates the alarm float. means of the push-button). . Checking after actuation of the relay When the signal is given, the colour of the gas should circuit be observed through the inspection-windows. • black gas is caused by free arcing in the oil. Draw a gas sample and analyse it by means of the If the relay disconnects the transformer, similar checks proper analyser. It should be noted that, usually: should be made to determine composition and quantity • whitish gas is caused by electric arcing in contact of gas collected by the equipment. with In any case never put back the transformer into service paper, cotton or silk without having detected the cause of fault and having • yellowish gas is due to wood and cardboard repaired it. • greyish gas is caused by a breakdown of the magnetic

Operating instructions MOUNTING INSTRUCTIONS : the Buchholz relay electrical circuits are connected it is advisable to effect is mounted on the connecting pipe between the the mechanical test of the alarm and trip circuits by transformer and the conservator: the arrow marked on means of the apposite button located on the relay’s the relay cover must point toward the oil conservator. cover. The pipe should not contain any right-angle elbow. Caution: gradually press the button until first alarm Pipe diameter should correspond to the diameter of the contact is obtained, and afterwards also the trip contact relay’s hole for the oil passage. The pipe must be is activated. The push-button is self returning thereby arranged to slope upwards towards the conservator at freeing the signalling devices of the relay as soon as an angle of 1/5 degrees to the horizontal. the pressing action upon the button is discontinued. ELECTRIC WIRING DIAGRAM : inside junction SIGNALLING : • in case of gas accumulation: alarm box cover it’s possible to find electric wiring diagram • in case of lack of oil: trip that consent the operator to effect the connection of the • in case of oil surge: trip relay to alarm and trip circuits and to the earth. Once BUCHHOLZ RELAY type BG 25 – DIN 42566

POS. DESCRIPTION 1-2 release terminals 3-4 alarm terminals 5 earth terminals 6 breather cock 7 valve of pneumatic test 8 mechanical test of the alarm/release circuit 9 cable gland PG 16 10 drain plug 11 plug PG 16

TYPE A B D E L S d1 gas vol. weight

BG 25 196 136 R11/2” BSP 140 185 16 25 150 cm3 2,5 Kg. BUCHHOLZ RELAYS types BR 25 /50/80 – DIN 42566

TYPE A B C D E L S d1 d2 d3 n° holes gas vol. weight BR 25 196 136 85 115 140 200 15 25 14 68 4 150 cm3 3,1 Kg. BR 50 250 168 125 165 140 195 18 50 18 102 4 250 cm3 4,5 Kg. BR 80 303 193 160 200 140 195 18 80 18 138 4/8 250 cm3 5,2 Kg. BUCHHOLZ RELAY type BS 25 – BS STANDARD

POS. DESCRIPTION 1-2 release terminals 3-4 alarm terminals 5 earth terminals 6 breather cock 7 valve of pneumatic test 8 mechanical test of the alarm/release circuit 9 cable gland PG 16 10 drain plug

TYPE A B C D E L S d1 d2 d3 n° holes gas vol. weight

BS 25 196 136 50,8 75 140 127 12 25 M10 - 4 200 cm3 2,6 Kg. BUCHHOLZ RELAY type BS 50-80 – BS STANDARD

POS. DESCRIPTION 1-2 release terminals 3-4 alarm terminals 5 earth terminals 6 breather cock 7 valve of pneumatic test 8 mechanical test of the alarm/release circuit 9 cable gland PG 16 10 drain plug

TYPE A B C D E L S d1 d2 d3 n° holes gas vol. weight BS 50 278 168 110 140 140 185 15 50 11 - 6 300 cm3 4,1 Kg. BS 80 293 183 130 160 140 185 15 80 11 - 6 400 cm3 4,4 Kg. FINISHED PRODUCT QUALITY CONTROL TESTS

BUCHHOLZ RELAYS

Hydraulic test for tightness for the body : the aluminium alloy casing is filled with oil at the temperature of 90°C and at the pressure of 300 kpa. After 4 hours no leakages must be observed. The same test is carried out for floats and switches.

Dimensional check .

Hydraulic test for tightness of the finished relay : the test is carried out by filling the Buchholz relay with oil at the temperature of 90°C and at the pressure of 200 kpa. Said test lasts 4 hours. During this period no oil leakage is ad- mitted.

Manual and pneumatic inspection of the electric contacts actuation: This test is carried out both on alarm and trip circuits . It’s performed by means of visual indicators mounted on a panel-board.

Check of tripping velocity : performed by mounting the relay on a oil filled pipeline. By means of a calibrated flow meter and of suitable visual indicators mounted on a panelboard .

Check of instrument mechanical protection degree : IP 54.

Isolation test : carried out by means of a microprocessor controlled testing unit.