Basler BE1-40Q demagnetization relay setting test

Current input: Connect the CT secondary circuit to the current input terminal, pay attention to polarity. The internal CT of the relay has an automatic short-circuit function - when the connecting plug is pulled out, the CT input terminal automatically shorts, avoiding the danger of CT open circuit.

Control power supply: Connect DC or AC power to the power terminals (such as terminals 3 and 4), without polarity requirements, but ensure that the voltage is within the allowable range (such as at least 14V for 24Vdc startup, and can be maintained as low as 12V).

Output contacts: The main output is used for tripping, and the auxiliary output is used for signaling. The wire diameter shall not be less than 14 AWG.

Grounding: The grounding terminal of the shell must be connected to the grounding grid with a copper wire of not less than 12 AWG, and independent leads are recommended.

EMI suppression: If the output contact drives the external relay coil, it is recommended to parallel reverse diodes (DC) or impedance capacitance absorption circuits (AC) at both ends of the coil to suppress electromagnetic interference when the contact is disconnected.

Insulation test warning: Before conducting a withstand voltage test, the connecting plug must be unplugged and the relay must be removed from the chassis, otherwise high voltage may damage the internal electronic components.

4. Setting calculation method and examples

The setting basis for BE1-40Q is the Capability Curve and static stability limit provided by the generator manufacturer. The setting goal is to place an 8 ° diagonal line below the intersection point of the capacity curve and the static stability limit, and calculate the intersection point value of the line with the Q axis as a unit, and then convert it into the specific gear of the panel TAP switch.

Setting steps (example):

Known: The rated apparent power of the generator is 100 MVA, the rated line voltage is 12.8 kV, the CT ratio is 5000/5, and the PT ratio is 12800/120.

Determine the minimum allowable reactive power absorption for demagnetization protection based on the capacity curve, assuming it is 0.4 pu of rated power (i.e. the three-phase transformer absorbs 40 Mvar).

Single phase reactive power=40/3=13.33 Mvar.

Convert the corresponding single-phase current: I=(single-phase reactive power × √ 3)/line voltage=(13.33 × 10 ^ 6 × 1.732)/12800 ≈ 1804 A (primary value).

Converted to CT secondary: Isec=1804/(5000/5)=1.804 A.

If the relay voltage is 120V (PT secondary), the required setting value (single-phase var) is (V_relay/√ 3) × I2/sec=(120/1.732) × 1.804 ≈ 125 var.

Refer to Table 1-1 (120V range LOW gear), 125 var corresponds to TAP position E (LOW gear, E is 125 var). If HI mode is selected, it corresponds to different ranges, but LOW mode meets the requirements here.

In practical engineering, a margin should be left for the setting value, usually taking 90% to 95% of the calculated value, to ensure reliable operation before the static stability limit. At the same time, it is necessary to consider the errors of PT/CT and the normal reactive power fluctuations of the system.

5. Panel operation and parameter setting

Main controls of BE1-40Q panel:

RANGE switch: HI/LOW two levels, switch internal CT ratio, and use TAP switch to achieve wide range setting.

TAP switch: 10 gears (A~K), corresponding to different var values. Specific values can be found on the panel label or in Table 1-1 of the manual.

TIME DELAY DIP: Two decimal digits, set to 0.1-9.9 seconds, with a step size of 0.1 seconds. If set to 00, it is an instantaneous action (<50ms).

Target reset button: Manually reset the target indicator that has been activated.

Output test button: Press with a non-conductive rod to manually excite the output relay for circuit verification.

Setting process:

Determine the TAP value and RANGE gear based on the tuning calculation.

Set a delay according to the system's requirements for time limits (such as setting the generator to 0.5-2.0 seconds to avoid system oscillation and external fault transients).

If instantaneous action is required, set the delay code to 00.

6. On site testing and verification methods

Before production or during regular calibration, it is necessary to conduct action value and delay tests on the relay. The following steps are based on the recommended test circuit in the manual (Figure 5-2).

6.1 Action value (Pickup) verification

Test circuit: The voltage source is connected to the voltage input terminal of the relay, and the current source is connected to the current input terminal, with adjustable phase between the two.

Set RANGE=LOW, TAP=A (minimum value), and set the delay to 10 (1.0s) to prevent frequent actions.

Apply rated voltage (120V/208V/240V depending on the model), adjust the phase of the current source to lag by 60 ° (simulate reactive power absorption).

Slowly increase the current until the PICKUP LED lights up, and record the effective voltage and current values at this time.

Calculate the actual single-phase var=(V/√ 3) × I, and compare it with the nominal value of the TAP gear in Table 1-1. The error should be within ± 2% or ± 0.1 var.