Buchholz Relay Catalogue b&w - Atvus Industriesatvus.in/Catalog/Gas_and_oil_operated_buchholz_relay.pdf · andutilizedby'Buchholz'manyyears back.Inaseriesofexperiments...

BUCHHOLZ RELAY

FEATURES

AT-101

(Gas & Oil Operated)25mm, 50mm, 80mm

n

nnnnnn

Castings treated against porosity through a special process.Unique internal design of 'housing' prevents false air traps on top of the relay.Well designed internal layout gives clear view of colour of gas inside the relay through glass window for fault analysis.Bucket type float design with inherent ability to withstand vacuum treatment of transformers.Built in test facility for checking continuity of both Alarm and Trip circuits.Anti-vibration custom built mercury switches give high stability against mechanical shocks and vibrations.ATVUS relays are approved by most of the consultants, Power Projects and Electricity Boards in India.

IN SERVICE TO THE TRANSFORMER INDUSTRY SINCE 1971

GOR-1 (25mm)

GOR-2 (50mm)

GOR-3 (80mm)

SRI

GENERAL WORKING

APPLICATIONS

Power Transformers are consideredto be a highly reliable type ofequipment, yet, in order to ensure thecontinuity of service that modernconditions demand, protectivedevices are required. The purpose ofsuch devices is to disconnect faultyapparatus before large-scale damageis caused by a fault to the apparatusor to other connected apparatus.Such devices generally respond to achange in the current or pressurearising from the faults and are usedfor either signaling or tripping thecircuits.

Protective devices in the ideal casemust be sensitive to all faults, simplein operation, robust for service andeconomically feasible. Consideringliquid immersed transformers, anear-ideal 'protective device' isavailable in the form of Gas and Oilrelay described here. The relayoperates on the well-known fact thatalmost every type of electric fault in a'liquid immersed transformer' givesrise to gas. This gas is collected in thebody of the relay and is used in someway or other to cause the alarm or thetripping circuit to operate.

The principle of the Gas and Oil relaywas first successfully demonstratedand utilized by 'Buchholz' many yearsback. In a series of experimentscarried out extensively in Germany itwas proved that the Relay is capableof bringing to light incipient faultthereby preventing further spreadingof the fault and extensive damage andthus saving expensive and protractedrepairs. So successful is the principleof this Relay that despite thecontinued search for better protectivedevices in other electrical fields theGas-and-Oil Relay is still on its own inproviding protection against a varietyof faults.

The function of a double elementrelay will be described here.

During normal operation of atransformer the Buchholz relay iscompletely filled with oil. Buoyancya n d t h e m o m e n t d u e t ocounterweights keep the floats intheir original top positions.

In the event of some fault in theinterior of the transformer tank, gasbubbles are produced whichaccumulate in the Buchholz relay onthe way to the conservator. Inconsequence, the oil level in the relayenclosure drops which in turn lowersthe upper bucket.

This causes the mercury switch tooperate an alarm signal.

The lower bucket does not change itsposition, because when the gasreaches the upper inside wall of thepipe it can escape into theconservator. Hence, minor fault in thetransformer tank will not trigger thelower switching assembly and willnot trip the transformer.

In case the liquid continues to dropdue to loss of oil, the lower bucketalso goes down. In consequence, thelower switching system operates ifthe level of oil goes below the bottomlevel of the pipe connected to therelay.

Alternately in the event the liquid flowexceeds a specific value (which iscontinuously adjustable, by means ofa flap) the lower bucket is forceddown, thus triggering the lowerswitching system to operate.

As the liquid flow rate decreases, orthe level of the liquid rises, the bucketreturns to its original position. Thesingle element relay has only Tripelement and it responds to only oil

surges. The method of operation issimilar to that described for doubleelement relay. Single element relaysare suitable for potential transformersand onload lap changers.

The single element oil Surge relay hasbeen specifically designed for usewith on load tap change equipmentand it will by-pass normal amounts ofgas which are generated by tapchange operations and will onlyrespond to oil surges and loss of oil.

Double element relays can be used indetecting minor or major faults in atransformer. The alarm element willoperate, after a specified volume ofgas has collected to give an alarmindication. Examples of incipientfaults are

(a) Broken-down core bolt insulation

(b) Shorted laminations

(c) Bad contacts

(d) Overheating of part of windings

The alarm element will also operate inthe event of oil leakage, or if air getsinto the oil system.

The trip element will be operated byan oil surge in the event of moreserious faults such as

(a) Earth faults

(b) Winding short circuits

(c) Puncture of bushings

(d) Short circuit between phases

The trip element will also be operatedif a rapid loss of oil occurs. Singleelement relays can be used to detecteither incipient or major faults in oilf i l led potent ia l transformers,reactors, capacitors etc. A specialsingle element relay is available forthe protection of on load tap-changeequipment.

BASIC CHARACTERISTICS

FUNCTIONAL TEST &ELECTRICAL CONNECTION

INSTALLATION& MAINTENANCEThe Gas and Oil Relay provides

protection against a number of internalfaults and is also able to indicate inseveral cases the type of fault. This ispossible because the gas collected inrelay can, from its colour, odour andcomposition, indicate where the faultmay be and what its nature is. Byexamining the gases collected it ispossible to infer the nature of fault.

Thus :

(a) If the gas is colourless andodourless or with only a faintodour of oil, the gas is air trappedin the oil or the insulation.

(b) If the gas is Greyish white withsharp and penetrating odour andnon-inflammable it is due tooverheated or faulty insulation(fuller board etc.)

(c) If the gas is Yellowish in colour andinflammable it maybe due tosurface leakage on material likewood.

(d) If the gas is dark Grey andinflammable it may be due to aflashover in oil or due to excessiveoverheating of the oil caused by afault in the winding or the core.

On the operation of the alarm ifinvestigation of the collected gas doesnot indicate a serious fault it ispossible to leave the transformer inservice till it is convenient to carry outa thorough inspect ion . Th isoccurrence is possible on a newlycommissioned transformer due to airtrapped in the oil or the insulation. Onrepeated and frequent alarm signalsthe transformer should be taken out ofservice for thorough check up.

A test system is provided in

the Buchholz relay that allows thefunctional test of the upper and lowerswitching system.

To test the relay function loosen the nuton the Test Key and rotate the key witha screwdriver in the anticlockwisedirection till the SLOT on the Test Keypoints towards the T/L position. Boththe alarm (upper switching system)and Trip (lower switching system) willshow continuity.

On bringing the SLOT on the Test Keyto S (service) position by rotating thekey clockwise the Alarm and Tripcircuits will not show continuity. Thecircuits will be actuated to 'ON'position only when there will a fault inthe transformer.

Repeat the functional test each time arelay is started or maintenancecompleted.

Screw the test pump tothe test cock.

Open the test cock and pump air gentlyinto the Buchholz relay until the upperswitching system operates.

For operating the lower switchingsystem air has to be pumped suddenlywith a jerk which will in turn operatethe lower switching system. The Tripelement may not operate with a cyclepump.

To allowinstallation of the 'single wire' open theterminal box cover comprising of thename plate and the instruction stickeron the backside. Then pass the wirethrough one of the three conduitscrewings into the terminal box. Theupper two studs are terminals for theAlarm switching circuit and aredenoted by A. Likewise the lower twostuds are terminals for the Tripswitching circuit and are denoted by T.

Forinstalling the relay into pipe-lineproceeds as follows :

To fillthe Buchholz relay, proceed asdescribed below :

The Buchholz relaysare not sensitive to external influences.No servicing is needed duringoperation. On routine inspections ofthe protection equipment, test thefunction of the Buchholz relay asdescribed earlier and check the alarmand trip devices connected to them.

Testing the relay Function with theTest Key :

Testing the relay function with theTest Pump :

Electrical Connection :

Installation into pipeline :

Filling with Insulation Liquid :

Maintenance :

l

l

l

l

l

l

l

l

l

l

l

See that the Buchholz relay ispositioned with the arrow pointingtowards the conservator, theconnection box is the Y Plan(Vertical) and the Test Cock. (1.7)and air vent cock (1.8) are at the top.

Mount the Buchholz relays as closeas possible to the tank in the pipelineb e t w e e n t r a n s f o r m e r a n dconservator.

Keep pipe bends as wide as possible.Avoid close bends.

Make sure pipe ascends to theconservator at angle between threedegrees to seven degrees.

See that the relay enclosure is notsubjected to stress. If necessary, useexpansion compensators.

Ensure that the slot on the Test Keyremains in the T/L (Test/Locking)position during storage or loosetransportation of the relay.

Ensure that the slot on the Test Keyremains in the 'S' (Service) positionand the Test Key Bolt is Tightened justbefore commissioning of the relay.

Remove the protective nut from the airvent cock.

Open the air vent cock to let air escapeuntil insulation liquid emerges.

Shut the air vent cock.

Check liquid level in conservator.

B

A

C

E

F

G

D

H

Due to our policy of continuous product improvement, dimensions and designs are subject to change.

No. Of Switching SystemsTransformer Rating (MVA)

Main Dimensions (mm)

Flange Dimensions (mm)

Pipe Bore (mm)Surge Test (TRIP) (cm/s)Gas Volume (ALARM) (cc)Velocity Test (cm/s)Element TestHigh Voltage TestInsulation Resistance TestPorosity TestMechanical Strength TestCurrent Rating of SwitchResistance of The Switch

2

below 1

250

128

205

1” Conduit

72

M 10

78 square

25

70 to 130

90 to 165

70 to 130With oil, at 1.4 Kg/cm for 15 minutes

2000 V at 50 Hz for 1 minuteGreater than 10 megaohms with 500 V meggar

With oil, at 1.5 Kg/cm for 4 hours

2

2

With oil, at 8 Kg/cm for 1 minute2 Amp at 240 V, 50 Hz AC/DC

Not to exceed 0.1 ohm across the electrodes of mercury switch

2

2

1 to 10

250

184 or 215

205

1”

115

18

150

50

75 to 140

175 to 225

75 to 140

Conduit

2

above 10

270

215

220

1”

145

18

185

80

90 to 160

200 to 300

90 to 160

Conduit

1

OLTC

170

119

200

3/4”

72

M 10

78 square

25

45 to 60

N.A.

45 to 60

Conduit

P.C.D.Holes / ThreadFlange Dia.

IS 3637, Clause 7.6IS 3637, Clause 7.5IS 3637, Clause 7.8IS 3637, Clause 7.4IS 3637, Clause 7.3IS 3637, Clause 7.3IS 3637, Clause 7.2IS 3637, Clause 7.7IS 3637, Clause 3.3IS 3637, Clause 3.3

A

B

C

D

E

F

G

H

RELAY TYPE

RELAY TYPEGOR 1

B

RELAY TYPEGOR 2 & 3

RELAY TYPESRI

GOR 1 GOR 2 GOR 3 SRI

INDUSTRIES689, Block ‘O’, New Alipore, Kolkata - 700 053, INDIA

Phones: (91-33) 24001101, 24009885 Fax: (91-33) 24007443, 24007043 E-mail: [email protected]

A

B

C

F DH

E

E

F

C

G

D

H