Monitoring Relays

EMB monitoring relays feature easy operation, high reliability and a very long life.

Type list

Monitoring relay for tap changers

The monitoring relay for tap changers, also known as the protection relay for tap changers or oil flow relay, is a monitoring device for insulating liquid-filled tap changers with conservators. It protects the tap changer and the transformer from damage. The monitoring relay responds to excessive oil flow in the direction of the conservator and generates a signal disconnecting the tap changer and the transformer immediately from voltage supply.

The monitoring relay is suitable for open-air as well as indoor installation.

General

We provide more than 45 years experience in producing monitoring relays and other protection devices for liquid-cooled and liquid-insulated appliances. It ranks among the most distinguished manufacturers of this type of equipment.

EMB monitoring relays feature easy operation, high reliability and a very long life.

Our staff of highly qualified engineers and experienced skilled workers ensures top quality and highprecision products. The casings are machined on modern CNC controlled machine tools. All products are subjected to final inspection when all functions are checked using special test equipment.

Profound experience and expertise in this special field are a sound basis for high product quality. Extensive references from reputed tap changer and transformer manufacturers as well as other users are proof of the high qualitative level of the products.

DESIGN FEATURES

Casing

The casing is made of weather-resistant cast aluminium alloy provided with a paint coat. To check the switching system for proper function, the casing is provided with sightglasses arranged opposite each other and protected by hinged lids (1).

Cover

The cover is made of weather-resistant cast aluminium alloy provided with a paint coat. The upper section of the cover accommodates the terminal box (1). The test and reset key covered by a cap nut (2), a screw plug (3) or, alternatively on customer’s request, a bleeder valve (see section 9. „Explanation on code 97“) are arranged in front of the terminal box. In addition a plate (4) with instructions for actuating the test and reset key is arranged there. The terminal box (1) accommodates the earth terminal (5) and the bushings (6) for the terminals provided in the base of the cover. The terminal box is sealed by an aluminium cap (7) so that it is safe to touch and protected against pollution. If the cap is opened the graphic symbol and the connection diagram (8) are shown. The cable is inserted through the cable gland (9).

Function

The monitoring relay is installed in the pipe between the tap changer and the conservator as close as possible to the tap changer head. During normal operation of the tap changer gases are generated which are collected in the gas dome of the monitoring relay. If the gas volume exceeds the volume of the dome, the gas flows in the direction of the conservator.

Fault: An incident causes an oil flow in the direction of the conservator.

Response: The liquid flow reaches the damper. If the flow rate exceeds the operating value of the
damper, the latter moves in flow direction.

This movement actuates a switch contact, and the tap changer and the transformer are
disconnected.

Technical data

Parameter	Data	Notes
Voltage	AC 5 V - max. 250 V DC 5 V - max. 250 V	Note max. switching capacity
Current	AC 0,01 A - max. 6 A DC 0,01 A - max. 6 A	Cos φ > 0,5 L/R < 40 ms note max. switching capacity
Switching capacity	AC max. 1500 VA DC max. 1250 W
Dielectric strength	AC 2500 V AC 2000 V (NO, NC) AC 1000 V (CO)	between electric circuit and earth between open contacts
Temperature range: Ambient temperature	- 40 °C to +55 °C - 40 °F to +131 °F	Climatic test acc. to DIN EN 60068-2-78: 2002-09 others on request
Temperature range: Operating range Temperature of insulating liquid	- 40 °C to +115 °C - 40 °F to +239 °F Up to + 135 °C requires version 21
Temperature range: Operating range Viscosity of insulation liquid	1 mm^²/s to 1100 mm^²/s
Insulating liquid	Mineral oil	Others on request
Resistance to vibration	Vibration: 2-200 Hz, 2 g Shock: 10 g, 11 ms
Resistance to pressure	0,25 MPa
Resistance to vacuum	< 2,5 kPa
Resistence to magnetic fields	25 mT	Magnetic balance in any direction and polarity
Switching system: Number of switching contacts Switching element Damper Response time of damper	1 Magnet contact tube Held by magnets < 0,1 s	See ordering data
Cable gland	M20 × 1,5; M25 × 1,5	Others on request
Nominal installation position	2° to 4°	Ascending towards conservator
IP code	IP 56	Others on request
Casing colour	2-component texture paint	On polyurethane basis

Options

Cable gland *

Explanation	Code
M20x1.5: 1 cable gland and 1 dummy plug	1
M25x1.5: 1 cable gland and 1 dummy plug	2
M20x1.5: 2 cable glands	3
M20x1.5: 2 cable gland and 1 dummy plug (enclosed)	3B
M25x1.5: 2 cable glands	4
M25x1.5: 2 cable gland and 1 dummy plug (enclosed)	4B
1/2“ NPT: 1 cable gland and 1 dummy plug	6
1/2“ NPT: 2 cable glands	7
Cable gland: on customer’s request	9

* Mandatory order data

Casing colour *

Explanation	Code
Casing colour RAL 7001 (silver-grey)	41
Casing colour RAL 7012 (basalt-grey)	42
Casing colour RAL 7022 (umber-grey)	43
Casing colour RAL 7033 (cement-grey)	44
Casing colour RAL 7038 (agate-grey)	45
Casing colour RAL 7035 (light-grey)	46
Casing colour RAL 7016 (anthracite-grey)	47
Casing colour RAL 9002 (grey-white)	48
Casing colour RAL 7032 (siliceous-grey)	49