Basler BE1-50/51B-255 Replacement CO Relay Guide

Basler BE1-50/51B-255 Overcurrent Relay: ABB CO Series Direct Replacement and Engineering Application Guide

Product positioning and replacement value

The BE1-50/51B-255 overcurrent relay launched by Basler Electric is a non directional overcurrent protection device based on microprocessor design, specifically designed for phase overcurrent or ground overcurrent protection in 50Hz or 60Hz power systems. This relay is equipped with three protective components: a timed overcurrent (51) component and two instantaneous overcurrent (50-A and 50-B) components, with the 50-B component used to implement the "Hot Line Tag" (HLT) function.

The most significant application value of BE1-50/51B-255 lies in its ability to directly replace ABB (Westinghouse) CO series electromagnetic overcurrent relays. Specific compatible models include CO-2 (short inverse time), CO-5 (long inverse time), CO-6 (timed), CO-7 (medium inverse time), CO-8 (inverse time), CO-9 (very inverse time), and CO-11 (extremely inverse time). The replacement operation is extremely simple - just set the required parameters on the new relay, unplug the original ABB relay plug-in core, insert the new core, close the blade switch, and install the new panel to complete the upgrade without changing the cabinet wiring.

Compared to traditional electromagnetic CO relays, the advantages of BE1-50/51B-255 include:

Extremely low CT burden: expands the linear working range of CT

Self powered operation: obtaining working power directly from induced current

Continuous automatic calibration: no need for internal manual adjustment

Gravity self-locking target indication: maintains motion indication even after power failure

Minimum transient exceedance: The instantaneous component effectively eliminates the exceedance caused by the transient component of the fault current

Core technical specifications

2.1 Timed overcurrent (51) component

Start value setting range: 0.5~15.9Ac (0.1A step)

Startup accuracy: ± 2% ± 25mAac sum

Exit ratio: 95% of the startup value

Characteristic curve type: Following IEEE standard C37.112 (1996), simulate GE IAC, Westinghouse CO, and BS142 curves

Curve types: Short inverse time, Long inverse time, Fixed time, Medium inverse time, Inverse time, Very inverse time, Extreme inverse time, BS142 Very inverse time, BS142 Extreme inverse time, Fixed timing (0.1~9.9s)

Timing accuracy: ± 1 cycle ± 2% within the range of 2~40 times the starting value; Within the range of 1.3 to 2 times the starting value, it is ± 2 cycles ± 2%

2.2 Instantaneous overcurrent (50-A) components

Start value setting range: 1~99Aac (1A step)

Startup accuracy: ± 2% ± 25mAac sum

Exit ratio: 95% of the startup value

Additional Delay: SW3-2 Switch Selection - No Additional Delay (OFF) or 100ms Fixed Delay (ON)

2.3 Transient Overcurrent (50-B/HLT) Components

Start value setting range: 1~15.9Aac (0.1A step)

Startup accuracy: ± 2% ± 25mAac sum

Exit ratio: 95% of the startup value

Delay characteristic: fixed as no additional delay

Reset feature: Reset within 16ms when the current drops below 95% of the starting value

2.4 Current sensing input

Continuous rating: 14Ac (below 45 ℃)

1-second rated: 400Aac

Input impedance: 4.4 Ω at 0.5A, 0.2 Ω at 5.0A

Frequency response: The change in starting current caused by a variation of ± 5Hz of the rated frequency is less than 0.5%

Harmonic suppression: The suppression characteristics of odd and even harmonics are shown in Figure 6-3

Transient response: When the system time constant reaches 40ms, it exceeds less than 10%

Control panel and configuration components

3.1 Front panel control and indication (Figure 2-1)

TIME PICKUP selector (two digit DIP): Set the timed overcurrent starting current value (ampere, integer and decimal)

INST PICKUP selector (two digit dialing): Set the instantaneous starting current value of 50-A (ampere, ten digit and one digit)

CURVE selector (10 position rotary switch): Select one of the 9 inverse time characteristics or fixed timing function (F mode)

TIME DIAL selector (two digit dialing): Select the delay multiple (00~99) on the selected curve

ACTIVE/PICKUP dual color LED: Green indicates that the relay has been powered on but not started; Red indicates that the induced current exceeds the set value for timed startup

Target indicator (gravity self-locking): Each of the 51 and 50-A components is equipped with a red target indicator, which needs to be manually reset

HLT switch: enable/disable hot wire marking function

HLT indicator light (red neon light): Illuminates when HLT is enabled and there is voltage in the trip circuit

Manual trip test socket: one pair of 51 element and one pair of 50-A element (for short circuit testing)

3.2 Internal circuit board switches and jumpers (Figure 2-2)

SW3 six position sliding switch:

SW3-1: System frequency selection (OFF=60Hz, ON=50Hz)

SW3-2:50-A additional delay (OFF=no delay, ON=+100ms）

SW3-3: Curve family selection (OFF=ABB CO type, ON=GE IAC type)

SW3-4: Reset feature selection (OFF=instantaneous reset, ON=integral reset)

SW3-5/6: Not used

50-B startup value setting switch (at the top of the movement, the movement needs to be pulled out for operation):

SW9 (16 bits): Set integer values (0~9 corresponds to 0~9A, A~F corresponds to 10~15A)

SW10 (10 bits): Set the decile (0~9 corresponds to 0.0~0.9A)

Target operating current jumper (J1/J2):

Crossing 1-2 pins: minimum operating current of 0.9~2.25A

Cross connect 2-3 pins: minimum operating current 80~200mA

Function description and working principle

4.1 Signal Process (Figure 3-1)

The single-phase AC current provided by the system CT is connected to the relay through terminals 8 and 9, and supplied to the power CT and signal CT respectively. The output of the power CT is rectified and filtered to provide working power for all circuits, with one precise 5VDC output serving as an automatic calibration reference.

The current output from signal CT is rectified and sent to three independent proportional resistor networks, which are controlled by the 51, 50-A, and 50-B starting value selection switches. The analog-to-digital converter converts the analog voltage on the proportional resistor into a digital signal and sends it to the microprocessor.

The microprocessor performs program operations based on induced current, switch settings, and internal software. When the induced current exceeds the TIME PICKUP set value, the ACTIVE/PICKUP LED changes from green to red, and the 51 timing element counts according to the characteristic curve equation; When the induced current exceeds the set value of INST PICKUP, the 50-A output contact immediately closes; When the induced current exceeds the set value of 50-B and the HLT switch is closed, the output contact of 50-B is closed.

4.2 Integral reset characteristics

The integral reset characteristic simulates the "disc reset" behavior of electromagnetic relays, starting timing when the current drops below 95% of the starting value, and continuing to work even if the current completely drops to zero. The reset time equation is:

T_R = R·D / (M² − 1)

Among them, TR is the reset time (seconds), R is the curve constant, D is the set value of the time dial, and M is the multiple of the current relative to the starting value. This feature is particularly important when used in conjunction with electromagnetic relays with thermal memory effects - it ensures that the relay "remembers" the accumulated heat from the previous fault during multiple reclosing processes, thereby achieving more accurate selective coordination.

Installation and wiring points

5.1 Directly Replace Installation Steps

Select the desired protection settings on the new BE1-50/51B-255

Pull out the core of the original ABB (Westinghouse) CO relay

Insert the new relay core and lock it in place

Close the blade switch

Install the new panel and secure it with the panel locking nut

5.2 Electrical Connections (Figure 4-1, 4-2)

Communication input: terminals 8 and 9 (current sensing input, 5A CT circuit)

51/50-A/50-B output contacts: terminals 1 and 10 (common trip output)

DC control circuit: see Figure 4-2 for typical wiring

When replacing the relay, due to the fact that all current input terminals of the BE1-50/51B-255 module are equipped with short-circuit wires when unplugged, it can ensure that the CT circuit does not open during the unplugging process, without the need for additional short-circuit operations.

5.3 Target Operating Current Setting

The target indicators for both the 51 component and the 50-A component are current excitation type, and their respective minimum operating current ranges can be set through circuit board jumpers J1 and J2 to adapt to different levels of trip circuit current.

5.4 Storage and Maintenance

The device contains long-life aluminum electrolytic capacitors inside. For long-term storage of backup equipment, it is recommended to run it on power for 30 minutes every year to extend the lifespan of the capacitor.

Complete on-site testing process

6.1 Testing Equipment Requirements

0~20Aac current source (induced input current)

DC power supply (target operation test)

Timer or counter

6.2 51 Component Startup Value Test

Connect the test circuit according to Figure 5-1

SW3-3=OFF (ABB curve), SW3-4=ON (integral reset)

Apply current to the ACTIVE/PICKUP LED turning red - the starting current should not exceed 0.55Aac

Reduce the current until the LED turns from red to green and then goes out

Set TIME PICKUP=2.2, slowly increase the current until the LED turns red - the current should be between 2.131 and 2.269Aac

6.3 Timing accuracy test

TIME PICKUP=1.0，TIME DIAL=4.5，CURVE=S

Apply 1.5Aac (1.5 times the starting value) and time until the 51st contact is closed

The timing value should be between 0.345 and 0.424 seconds (this tolerance is the cumulative starting and timing tolerance)

6.4 Integral Reset Test

TIME DIAL=9.9，CURVE=V，TIME PICKUP=1.0

Apply 4.0Aac to the relay and remove the current for 29 ± 0.25 seconds

Apply 4.0Aac again and time until the second action - it should be 2.08 ± 0.4 seconds

6.5 50-A Instantaneous Start Value Test

TIME DIAL=0.0，CURVE=S，TIME PICKUP=15.0

Set INST PICKUP=02, slowly increase the current to close the 50-A contact - the current should be between 1.935 and 2.065Aac

Set INST PICKUP=08, increase current to contact closure - current should be between 7.815~8.185Ac

6.6 50-B Instantaneous Start Value Test

The setting value of 50-B is set through the SW9/SW10 at the top of the movement. This step tests the 2.0A and 8.0A gears in sequence

The verification value is the same standard as the 50-A test (starting value ± 2% ± 25mA)

6.7 Target indication test

Connect the DC power supply to the output contact circuit according to Figure 5-2

Apply 2Aac induced current to close contact 51, slowly increase the DC power supply to the target action - verify that the action is within the jumper setting range

50-A target similarity test

6.8 HLT functional testing

50-B set value=2.0A, HLT switch on

Apply 3Aac induced current → 1-10 contacts should not close

Close the HLT switch, and the HLT indicator light should light up

Apply 3Aac induced current → 1-10 contacts should be closed immediately

6.9 Manual Trip Test

Warning: The front panel test socket has a tripping circuit voltage, and insulation jumper must be used during testing.

Apply 0.9Aac (provide working power but below startup threshold)

Short circuit the 51 manual trip socket → Verify that the timer detects the closure of the 51 contact

Short circuit the 50-A manual trip socket → Verify that the timer detects the closure of the 50-A contact

Characteristic curve and setting calculation

7.1 Timing characteristic equation

The timing characteristics of BE1-50/51B-255 are defined by the following equation:

T_T = A·D / (M^N − C) + B·D + K

T: Action time (seconds)

D: Time dial setting value

M: Multiple of current relative to the starting value

A. B, C, N, K: constants of specific curves (see Table 7-1/7-2)

The constant selects the curve family (ABB CO type or GE IAC type) through switch SW3-3, covering a range of 1.3-40 times the starting value.

7.2 Integral reset equation

T_R = R·D / (M² − 1)

TR: Reset time (seconds)

R: Curve specific constant

D: Time dial setting value

M: Current multiplier during reset period (M=0 when it drops to 0, negative value indicates complete reset)

7.3 Coordination and Cooperation Calculation Example

In a typical feeder protection coordination scheme, if BE1-50/51B-255 adopts ABB CO-11 inverse time limit curve, the cumulative effect of action time during multiple reclosing processes can be calculated using the integral reset characteristic when cooperating with upstream electromagnetic relays. When D is set to 2, the full action time at 10 times the startup value is 0.209 seconds, and the full reset time is 15.5 seconds. If there is a coincidence 3 seconds after the first trip, the second action time is only 0.040 seconds; The third time (cumulative reset time 11.96 seconds) is 0.161 seconds, fully reflecting the engineering value of the integral reset characteristic in the reclosing coordination.

Common troubleshooting guide

Troubleshooting direction

ACTIVE/PICKUP LED does not light up. Check if the induced current is less than 0.5A (minimum LED lighting current); Is the CT circuit open or wired incorrectly

Check if the TIME PICKUP set value is much higher than the actual current when the LED green to red does not convert; Is the startup value set accurately

Confirm whether the selection of the SW3-3 curve family is consistent with the curve graph used when the timing action time deviation exceeds the tolerance; Does the TIME DIAL dial correspond to the correct position; Test whether the current is a precise multiple

Check if INST PICKUP is mistakenly set to 00 (which will affect timing calibration) during the 50-A momentary inactivity check; Has the induced current reached the set value; SW3-2 delay switch status

Is the HLT switch closed when the 50-B does not operate; Is the starting value of 50-B higher than the actual current; Is the SW9/SW10 setting accurate? (Note that A~F correspond to 10~15A)

Check if the J1/J2 jumper position matches the tripping circuit current level (80~200mA or 0.9~2.25A) when the target does not move; Does the output circuit current meet the minimum requirements

Whether the gravity self-locking target does not reset and the target reset button is pressed properly; Is the mechanical mechanism jammed

After replacing the ABB relay, if it does not close, confirm whether the blade switch of the new relay has been tightly closed; Is the panel locking nut securely in place; Has the CT short-circuit reset when the old relay is pulled out

Check if the SW3-3 position (OFF=ABB CO type, ON=GE IAC type) is consistent with the matching logic for abnormal coordination with GE relays