Buchholz relay

The Buchholz relay is an important protection and monitoring device for insulating liquid filled-transformers with conservators and choke coils. It also allows separate monitoring of oil-filled bushings or cable terminal boxes.

It is mounted in the cooling cycle of the appliance to be protected
and responds to faults such as gas generation, loss of insulating liquid and excessively high flow rates of the latter.

Buchholz relays are available in a number of types which comply
with norms and standards and meet special customer requirements. The type of relay to be used depends on the nominal rating and construction features of the appliance to be protected. Our range of products permits optimum flexibility.

EMB Buchholz relays comply with DIN EN 50216-2 and are known for
their easy operation, high reliability and extremely long life.

Pipe diameter DN: 25 mm (1“), 50 mm (2“), 80 mm (3“)
Type of connection: threaded or flanged

Selected technical data:

Voltage: AC/DC 5 V to max. 250 V
Current: AC/DC 0.01 A to max. 6 A 
Ambient temperature: - 40°C to + 55°C 
Climate-proof version: extreme frigid open-air conditions below -40°C;
Offshore and aggressive industrial atmosphere
IP code: IP 56 or 66

Response of the switching system in the case of:
- Gas accumulation: 200 to 300 cm3
- Insulating liquid flow: damper setting:
  min. 0.65 to max. 3.00 m/s +/- 15%

Damper: held by magnets
Switching element: magnet contact tube
Contact setting of the switching system: normally-open contact,
normally-closed contact, change-over contact

Buchholz relay equipped with up to five magnet contact tubes
(see catalogue for switching design options)

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