Numerical under frequency relay - Armo Electronics and Electricals (India)

Numerical under frequency relay

TYPE UFT-21/UFT-31/UFT-41

A switch is provided to select either an independent made of operation of three or four channels or select the under/over frequency made of operation.

The test switch, tripping indications & reset button are provided on the front of Relay.

The relays are suitable for any application in industrial plants & to generators where definite time under/over frequency protection is required

Internal timers are provided for each operating circuits & separate aux. Relays ensure maximum flexibility of operation.

Internal event recording of last three event. The values of parameters at the moment of tripping are recorded on the display.

Two terminals are provided for the voltage input to the frequency sensing circuit the measurement of the frequency is digital for which only the zero crossing of the system voltage & not its amplitude are of consequence the relay is independent of the voltage fluctuations with a wide range. However the system voltage sink below a predetermined value in which the accurate measurement can no longer be expected the under voltage blocking circuit blocks all the outputs.

Operations of the relay can be tested by means of a test, button which energies the output relays & LED’s after set time delay with the channels set to under/over frequency operation. Access to the test push button requires removal of the front cover. This test facility should normally only be used with the relay trip circuits isolated

TECHNICAL DATA

AC voltage rating	110,220 VAC
Auxiliary supply voltage	30-220 V DC
Frequency setting range	39.00 to 70. 00 Hz in step of .1Hz
Operating voltage range	33 to 135 V the relay is block below this limit
No of tripped stage	2 for UFT -21 3 for UFT -31 4 for UFT- 41
Reference frequency	4 MHZ
Accuracy	+ .03 Hz
Reset Ratio	100%
Timer Range	.05 to 7.35 Sec. for under & over Frequency stage.
Burden
Aux Supply from PT	1.5 VA

Aux Supply from external source	1.5 VA max at 150 V
Aux DC (without tripping relays)	11 W for 4 stages
Contacts in relay	3 pair of N/O contact make & carry 7500 VA for 0. 25 with maxima of 30 A & 300 VAC or DC Carry contentiously 5 A AC/DC. Break 1250 VA AC/50 W DC resistive, 25 W L/R = 0. 04 S. Subject to maxima of 5A & 300 V
Test Voltage	2 kv/50 Hz 1 min. 5kv 1.2/50 us
Reduced values are valid in case of repeat testing casing	Does not apply to the terminal connected to a common Aux supply.
Casing	Flush mounting with rear connection 96x 192 / 192 x 192 x 200/250 mm W H D
Guaranteed operation	– 10 + 55° C

UNDER FREQUENCY RELAY & FREQUENCY TREND RELAY
INSTALLED BY US

MSEB	Wardha, Nagpur, Amravati, Kalwa, Aurangabad, Chandrapur, Nashik, Bhiwandi, Bhusawal, Akola, Kolhapur
Mula Pravara Electric Co.	Ahmednagar

Features

Low Burden
Wide operating voltage range
Wide frequency setting range 39. 00 to 70. 00 Hz
Independently adjustable tripping stages.
Consistent accuracy (± .03 Hz)
Unaffected by voltage fluctuations
Insensitive to harmonics & transient
Built in timer(.1 to 99.9 Sec.)
Built in event recorder for last three events.
Under frequency & over frequency relay with 2 to 4 frequency stages.
Adjustable under voltage blocking level.
Field Adjustable relay rated frequency
One operate time can give to each frequency stage.
Protection stages can be separately blocked via internal blocking inputs.

Application

ARMO UFT frequency relays are used to monitor the frequency of an electrical system. Due to inadvertent splitting of inner connection in power system, isolated areas of the system may become deficient in the generation & frequency of the same may drop considerably giving rise to emergency conditions. In order to maintain control of system tinder this low frequency emergency some form of grated load shedding in needed.

ARMO UFT relay is used to detect such condition & initiate load shedding to prevent complete system collapse.