Buchholz Relays | Protection of Oil Filled Transformers

Buchholz Relays By Pbwel

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

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

Data Sheets