Answer / ganesan.n

Bucholz Relay is an relay gives alarm for small faults, and
gives trip signal while a big fault happens!! There will be
a float inside the ball accoring to the fault level some
amount of gas will be produced if the fault is small that
float touches the switch of alarm otherwise it closes the
trip circuit!!

Answer / manish meena

bucholz relay is oil and gas operated protective relay
which is mounted on the pipe between transformer tank and
conservator
so when during any fault result in gas formation this will
cause the oil level in relay to drop and makes the alarm
contact to operates if the fault is very severe then the
gas formation will be very large due to this there is
further decrease in level of oil in relay..due to this trip
contacts are operated and finally the transformer is
disconnected from the supply....

Answer / valluru subba rao

Buchholz Relay (found only on transformers with conservators).
The Buchholz relay has two oil-filled chambers with floats
and relays arranged vertically one over the other. If high
eddy currents, local overheating, or partial discharges
occur within the tank, bubbles of resultant gas rise to the
top of the tank. These rise through the pipe between the
tank and the conservator. As gas bubbles migrate along the
pipe, they enter the Buchholz relay and rise into the top
chamber. As gas builds up inside the chamber, it displaces
the oil, decreasing the level. The top float descends with
oil level until it passes a magnetic switch which activates
an alarm. The bottom float and relay cannot be activated by
additional gas buildup. The float is located slightly below
the top of the pipe so that once the top chamber is filled,
additional gas goes into the pipe and on up to the
conservator. Typically, inspection windows are provided so
that the amount of gas and relay operation may be viewed
during testing. If the oil level falls low enough
(conservator empty), switch contacts in the bottom chamber
are activated by the bottom float. These contacts are
typically connected to cause the transformer to trip. This
relay also serves a third function, similar to the sudden
pressure relay. A magnetically held paddle attached to the
bottom float is positioned in the oil-flow stream between
the conservator and transformer tank. Normal flows resulting
from temperature changes are small and bypass below the
paddle. If a fault occurs in the transformer, a pressure
wave (surge) is created in the oil. This surge travels
through the pipe and displaces the paddle. The paddle
activates the same magnetic switch as the bottom float
mentioned above, tripping the transformer. The flow rate at
which the paddle activates the relay is normally adjustable

Answer / tukoweke

The relay serves to detect a fault in a transfomer that is
leading to the decomposition and accumulation of gas in the
tx or leakage of oil thus lowering the oil level, by making
contacts in the float and sending an alarm signal.

In case the fault persists and the gas accumulation
increases or when an arc takes place in the tx windings,
the oil surges up into the conservator tank and makes
contacts in the float/vane to send a message to the trip
coil of the breaker, thus isolating the transformer from
further damage by the fault.

Answer / pandi tom

The operation of buchholz relay is as follows:

i. In case of slow developing faults within the transformer, the heat due to the fault

causes decomposition of some transformer oil in the main tank. The products of decomposition mainly contain 70 % of hydrogen gas. The hydrogen gas being light tries to go into the conservator and in the process gets trapped in the upper part of the relay chamber. When a predetermined amount of gas gets accumulated, it exerts sufficient pressure on the float to cause it to tilt and close the contacts of mercury switch attached to it. This completes the alarm circuit to sound an alarm.

ii. If serious fault occur in the transformer, an enormous amount of gas is generated in

the main tank. The oil in the main tank rushes towards the conservator via the buchholz relay and in doing so it tilts the flap to close the contacts of mercury switch. This completes the trip circuit to open the circuit breaker controlling the transformer.

Answer / deshraj

Buchholz Relay is designed for protection of Oil-filled
Transformers, Capacitors, On-load Tap chambers etc. fitted
with conservator. The generation of gas in such equipment is
a sign of electrical malfunction. During minor faults
presence of gas triggers an Alarm, and during major faults
oil surge is developed due to rapid formation of gas
resulting in total disconnection by operating Trip circuit
of relay.

Answer / ajay

bucholz relay amounted on transformer
betn oil tank & transformer &provide the protection to
transformer from minimum oil.

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