ÜRF — OLTC protective (oil-flow) relay for transformers with on-load tap changers
The ÜRF oil-flow protective relay is installed in the pipe between the OLTC diverter switch compartment and the oil conservator and trips the tap changer and the transformer in the event of an internal fault in the diverter switch. The range covers types 12, 15 and 16 for nominal bore DN 25 or 28 mm, weight 3.6–4.0 kg. The relays are used in outdoor and indoor substations.
- Types
- 12 (ÜRF 25/10), 15 (ÜRF 25), 16 (ÜRF 25/10-26)
- Nominal bore
- DN 25 (type 16 — 28 mm)
- Flow velocity setting
- on request (example — 2.00 m/s)
- Flap operating time
- < 0.1 s
Price, availability and lead time on request. We help with analogue selection, customs clearance and delivery.
Description
The ÜRF Monitoring Relay, also known as an OLTC protective relay or oil-flow relay, protects oil-filled on-load tap changers with an oil conservator. Its purpose is to prevent an internal fault in the OLTC diverter switch from destroying the tap changer and the transformer itself. EMB has manufactured these relays in Barleben since 1965, and together with Buchholz relays the company has sold more than 1.5 million units. The relay is mounted as close as possible to the tap changer head, the pipe to the conservator is laid without elbows at a rise of 2–4°, and the red arrow on the housing must point towards the conservator.
The operating principle takes into account a specific feature of the OLTC. Every switching operation produces switching gases, which collect in the gas dome of the relay and, once it is full, escape to the conservator. Therefore, unlike a Buchholz relay, the ÜRF does not respond to normal gas generation. In the event of a fault in the diverter switch, an oil surge towards the conservator occurs. It presses on the flap held by a magnet, and once the setting is exceeded the flap swings, closes the contact and trips the OLTC together with the transformer in less than 0.1 s. The flow velocity setting is specified with the order, for example 2.00 m/s. The flap adjusting screw is not touched after factory setting.
The range consists of type 12 (ÜRF 25/10) and type 15 (ÜRF 25) with DN 25 flange connection, and type 16 (ÜRF 25/10-26) with a 28 mm bore. The housing and cover are cast from weather-resistant aluminium alloy and machined on CNC machines, and the inspection windows have hinged covers. A test and reset button is located on the cover, and an air vent valve (code 97) is fitted on request. The terminal box contains reed contacts, and the cable is routed through M20/M25 or 1/2″ NPT glands. Each relay undergoes a functional test on dedicated test benches before shipment.
The contacts switch AC/DC 5–250 V at a current of 0.01–6 A, the switching capacity is 1500 VA/1250 W, and the dielectric strength is 2500 V. The relay operates at ambient temperatures of −40…+55 °C and oil temperatures of −40…+115 °C, withstands vibration of 2–200 Hz/2 g and shock of 10 g/11 ms, and has IP56 degree of protection. For vacuum-type tap changers, where a gas accumulation alarm is also required, type 16 is combined with the EMB type 06 Buchholz relay (BF 25/10) in a single transformer gas protection scheme.
Technical specifications
| Types | 12 (ÜRF 25/10), 15 (ÜRF 25), 16 (ÜRF 25/10-26) |
|---|---|
| Nominal bore | DN 25 (type 16 — 28 mm) |
| Flow velocity setting | on request (example — 2.00 m/s) |
| Flap operating time | < 0.1 s |
| Contacts | AC/DC 5–250 V, 0.01–6 A; 1500 VA / 1250 W |
| Vibration resistance | 2–200 Hz, 2 g; shock 10 g, 11 ms |
| Liquid temperature | −40…+115 °C |
| Mounting rise | 2–4° towards the conservator |
| Degree of protection | IP56 |
| Weight | 3.6–4.0 kg |
Replacement for
РСТ-25, РСТ-80 (OLTC oil-flow protective relays), URF 25/10
selected by purpose and main parameters, please confirm with our manager
Request a price and lead time
ÜRF — OLTC protective (oil-flow) relay for transformers with on-load tap changers. We reply within one business day.
Or email sales@usk.ua or call 044 339-50-20.
Customs codes
| UKTZED (Ukraine) | 8536 49 00 00 |
|---|---|
| HS, 6 digits | 8536 49 |
| CN (EU) | 8536 49 00 |
| HTSUS (USA) | 8536 49 00 85 |
| China customs tariff | 8536 49 00 00 |
Codes are for reference: the final code is determined at declaration for the specific model.
Questions and answers
What nominal bore is the ÜRF relay designed for?
Types 12 and 15 have a DN 25 flange connection, type 16 is designed for a pipe with a 28 mm bore. The relay weighs 3.6–4.0 kg.
Why does the relay not operate on gases released during OLTC switching?
Switching gases collect in the gas dome of the relay and, once it is full, escape to the conservator. The relay responds only to an oil flow whose velocity exceeds the setting, for example 2.00 m/s.
What can replace the РСТ-25 relay on a transformer with an OLTC?
The ÜRF performs the same OLTC oil-flow protection function and is installed in the DN 25 pipe between the diverter switch and the conservator. The type and setting are selected according to the application and connection dimensions; agree the final choice with the manager.
Other analogues
European analogues of РСТ-25, РСТ-80 from other manufacturers and series.
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