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Protector trip relay - Crompton Instruments - 250 Series - Reverse Power (current)
Features
- Three-phase, three or four-wire
- Adjustable set point
- Adjustable time delay
- Internal differential
- LED trip indication
- Double-pole relay contacts
- Automatic reset
Benefits
- Current and power factor measurement
- Protects generators against ‘motoring’
- Detects reverse power under fault conditions
- Customised options
- Nuisance tripping avoidance
Applications
Marine panels
- Switchgear
- Distribution systems
- Generator sets
- Control panels
- Process control
- Motor protection
- Transformers
- Overload protection
Operation
Reverse power protectors provide continuous surveillance of ac generators against motoring. Reverse power relays are used to detect the failure of the prime mover (engine) when active energy (Watts) flows into the generator causing rotation – the set will operate like an electric motor which can cause significant mechanical damage. This relay offers an adjustable reverse power set point between 2% and 20% of nominal power and time delay adjustment range of 0 to 20 seconds.
As soon as the reverse power level increases above the set point limit, the time delay is activated, after which a trip will occur. The time delay prevents the relay from tripping for a predetermined period to prevent nuisance tripping. The products also feature an internal differential (hysteresis) setting of 1% to reduce nuisance tripping if the measured signal is noisy or unstable. These units are powered from the measuring supply.
The protector relay estimates the power level in the system by measuring current and power factor, but does not actually measure the system voltage. When the reverse power level exceeds the set point, the time delay is started. When the time has elapsed, the relay will energise and the red LED will illuminate to indicate the trip condition. The relay will automatically re-set once the power level falls
below the set point minus the differential. The LED will extinguish and the relay de-energises.
The time delay is not active when resetting. The reverse power level will trip as expected at the calibrated point for unity power factor. However, the system power factor does affect the trip point calibration. The relay becomes more sensitive at lagging power factors, as almost all systems exhibit inductance. At leading power factors, this relay is less sensitive.
Setting Up
The ‘% set’ potentiometer trimmer on the front label is calibrated as a percentage of the input current rating e.g. of 5A and not of the forward kW. Adjust the ‘% set’ trimmer to the required tripping value, 7.5% to 10% is normal. Setting accuracy can be checked by reversing the current lead connections and, with forward power, measuring the trip point value on a suitable ammeter (reconnect leads on completion). Adjust the ‘Delay’ to the required time delay, 10 seconds is normally adequate.
Options
250 series protector relays offer various customised options to suit individual requirements. Please consult factory.
- Adjustment ranges – different adjustment ranges are possible for the set point and time delay controls.
- Relay operation – standard models are fail safe, but the relays can be customised to de-energise on trip.
Product Codes
Relay |
Protection |
ANSI no. |
Cat. no. |
1-phase or 3-phase 4-wire |
Reverse power 2 – 20% |
32 |
256-PAS |
|
|
|
|
1-phase or 3-phase 4-wire. Push to test |
Reverse power 2 – 20% |
32 |
256-PAQ |
|
|
|
|
3-phase 3-wire. Push to test |
Reverse power 2 – 20% |
32 |
256-PAR |
|
|
|
|
3-phase 3-wire |
Reverse power 2 – 20% |
32 |
256-PAT |
Please specify system voltage, frequency and required options at time of ordering.
Specification – Reverse Power (Current)
Nominal voltage |
100V, 110V, 120V, 220V, 230V, 240V, 277V, 380V, 400V, 415V, 440V or 480V |
Nominal current |
5A or 2, 3, 4, 6, 8 and 10A |
System frequency |
50, 60 or 400Hz |
Burden |
Voltage: 3VA maximum |
|
Current: 2VA maximum |
Current overload |
2 x rating continuously, 10 x rating for 3 seconds |
Voltage overload |
1.2 x rating continuously, 1.5 x rating for 10 seconds |
Monitoring range capacitive |
Power factor: 0.5 inductive/unity/0.2 capacitive |
|
Current: 20 to 100% of nominal input |
Set point repeatability |
>0.5% of full span |
Differential (hysteresis |
Pre-set at 1% |
Trip level adjustment |
2 to 20%. Customised adjustment available |
Time delay adjustable |
0 to 20 seconds |
Output relay |
2-pole change over |
Relay contact rating |
AC: 240V 5A, non inductive |
|
DC: 24V 5A resistive |
Relay mechanical life |
0.2 million operations at rated loads |
Relay reset |
Automatic |
Operating temperature |
0°C to +60°C (0°C to +40°C for UL models) |
Storage temperature |
–20°C to +70°C |
Temperature co-efficient |
0.05% per °C |
Interference immunity |
Electrical stress surge withstand and non-function to ANSI/IEEE C37 90a |
Enclosure style |
DIN-rail with wall mounting facility |
Material |
Flame retardant polycarbonate/ABS |
Enclosure integrity |
IP50 |
Dimensions |
150mm (5.9") wide x 70mm (2.8") high x 112mm (4.4") deep |
Weight |
1.0Kg approx. |
Connections
256-PAS
256-PAT
256-PAQ
256-PAR
Note: Only one CT connection is required, from the same phase as the voltage connection to terminal 2.
Dimensions
Model 256
Danh mục sản phẩm
System |
Input |
Protection |
Catalog Number |
Reverse Power |
1 ph or 3 ph, 4w |
5A, 120V, 60 Hz |
Reverse Power 2-20% |
256-PASU-LSBX-PQ-C6-EA |
3 Phase, 3 Wire |
5A, 120V, 60 Hz |
Reverse Power 2-20% |
256-PATU-LSBX-PQ-C6-EA |
1 ph or 3 ph, 4w, Push |
5A, 120V, 60 Hz |
Reverse Power 2-20% |
256-PAQU-LSBX-PQ-C6-EA |
3 ph 3w Push |
5A, 120V, 60 Hz |
Reverse Power 2-20% |
256-PARU-LSBX-PQ-C6-EA |