Buchholz Relays | Protection of Oil Filled Transformers

Buchholz Relays By Pbwel

Buchholz Relays

Protection of Oil Filled Transformers | Large UK Stocks | Competitive Prices

PBwel Buchholz Relays are one of the few true cast body types in the world, developed in conjunction with the British Central Electricity Generating Board (CEGB).

PBwel offers a range of relays for small and mid-size transformers, many of which are used in substations across the world with an excellent track record of service.

Many relays remain in service after 50+ years satisfactory monitoring and PBwel have a proven track record of designing new solutions for any transformer protection required – form part of PBwel.

PBwel offer a range of single and double element type relays as part of their MV & HV Electrical Products as well as a range of relays accessories such as dry air pump, oil and gas sampling kits and diode protection units.

Buchholz Relays

Most faults in an Oil Filled Transformer are accompanied by the generation of gas.

By using a suitable relay, the formation of gas can be used as a warning of a developing fault.

Once a specified volume of gas has collected within the relay, the alarm element will cause an alarm indication.

If there is a more serious fault within the Transformer, the trip element will function. The trip element will cease the functioning of the Transformer to protect it from further damage, and protect those working around it.

Possible Causes for Alarm Indication

Broken-down core bolt insulation
Shorted laminations
Bad contacts
Overheating of part of the windings

Possible Causes for Relay Trip

Earth faults
Winding short circuits
Puncture of bushings
Short circuits between phases

Buchholz Relays Product Range

Buchholz Relays | Reed Switch Type Relays
Buchholz Relays | Mercury Switch Type Relays
Buchholz Relays | Single Element & Tap-Changer Type Relays
Testing Buchholz Relays Using Dry Air Pumps

Mounting Position

The Buchholz Relays should be mounted in the connecting pipe between the transformer and conservator tank. This pipe should be as long and as straight as possible, and must be arranged to slope upwards, towards the conservator at an angle within the limits of 3 to 7 degrees to the horizontal.

Buchholz Relays Characteristics

	Steady Oil Flow (mm/sec) to operate trip element switch		Oil level (cc) to operate Alarm Element Switch @ 500 Inclination
Model	Pipe angle 1º Not less than	Pipe angle 9º Not more than	Min	Max	For equipment containing
1SE	650	900	140	200
1SE/VO	650	900	120	160
1SE/VK/ML	900	1050	150	230
1SET	450	600	N/A	N/A
1SET/VO
1SET/HF	650	750	N/A	N/A
1DE	1000	1300	200	300	Up to 1000 litres 1000 kVA
1DE/VO
1DE/Vc/o
2DE	1100	1400	200	300	1001/10,000 litres 1001/10,000 KVA
2DE/VO
2DE/Vc/o
3DE	1200	1600	200	300	10,000/50,000 litres 10,001 KVA/99 MVA
3DE/VO
3DE/Vc/o
3DE/HF2	1900	2500	250	350	50,000 litres + 100 MVA
3DE/HF2/VO

See images in attached pdf for further information on the below table – Click here

Type	Dims	A	B	C	D	E	F	G	H	J	K	L	M	N
1DE	mm	127	269	232	171	98	76	114	72	76	25	–	–	–
	in	5.0	10.6	9.13	6.75	3.9	3.0	4.5	2.84	3.0	1.0	–	–	–
2DE	mm	184	269	232	158	111	76	114	110	139	51	13	–	–
	in	7.25	10.6	9.13	6.2	4.37	3.0	4.5	4.33	5.5	2.0	0.5	–	–
3DE	mm	184	269	234	158	111	80	114	130	160	76	13	–	–
	in	7.25	10.6	9.21	6.2	4.37	3.15	4.5	5.12	6.31	3.0	0.5	–	–
1SE	mm	120	174	212	110	64	76	103	72	76	25	–	3.0	22
	in	4.75	6.85	8.35	4.33	2.52	3.0	4.0	2.84	3.0	1.0	–	0.13	0.85
1SET	mm	120	174	212	104	70	76	103	72	76	25	–	3.0	22
	in	4.75	6.85	8.35	4.1	2.75	3.0	4.0	2.84	3.0	1.0	–	0.13	0.85

PBwel is a globally recognised designer, manufacturer and supplier of temporary portable earthing, voltage detectors, Buchholz relays and electrical safety products.

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