BENDER WR Transformer Selection

It should be noted that although the SP type enhances anti-interference ability, basic specifications still need to be followed during installation. The shielding layer and PE conductor must not pass through the inner hole of the transformer, otherwise it will damage the principle of residual current measurement. All current carrying conductors, including phase and N-wires, must pass through in the correct direction simultaneously. For three-phase systems, L1, L2, L3, and N should all pass through; For single-phase systems, L and N should pass through simultaneously. If only a portion of the conductor is passed through, the residual current vector sum will no longer be accurate, resulting in measurement distortion. For busbar systems, busbars are usually wider, and during installation, it is important to ensure that the busbars are aligned with the center of the transformer holes to avoid measurement errors caused by eccentricity.

Collaboration with RCM, RCMS, EDS systems

The WR series transformers can be compatible with various BENDER evaluation devices. RCMS460/490 and RCMS420 series residual current monitoring systems are suitable for centralized monitoring of multiple circuits; The RCM series residual current monitor is suitable for single circuit or small systems; EDS470, EDS460/490, and EDS440 insulation fault locators are used for IT system branch positioning. The connection method usually uses a two-wire cable, connecting the S1 (k) and S2 (l) terminals on the secondary side of the transformer to the corresponding input terminals of the evaluator. When wiring, pay attention to polarity, and the P1 (K) and P2 (L) directions should be consistent with the requirements of the evaluator. Wrong direction can cause the phase of the positioning current to be reversed, affecting the judgment of the faulty branch.

In the insulation fault location system, the positioning current injected by IRDH or PGH will return along the fault branch. WR transformers are installed on each branch to measure the positioning current. If there is an insulation fault in a certain branch, the transformer of that branch will detect a strong pulse signal, and the EDS evaluator will judge the fault channel based on this. The sensitivity, accuracy, and anti-interference ability of WR transformers directly affect the success rate of positioning. Therefore, in the positioning system, the transformer should be as close as possible to the monitored branch to avoid multiple branch cables crossing the same transformer, otherwise it is impossible to distinguish the faulty branch.

Interpretation of Key Technical Parameters

The technical parameters of WR series measuring current transformers determine their applicable boundaries. Its insulation coordination complies with IEC 61869-2, with a maximum system voltage Um of AC 720 V and a rated impulse withstand voltage Uimp of 3 kV. The rated transformation ratio of the measurement circuit is 600/1, the rated load is 180 Ω, the rated primary current is ≤ 10 A (100 A), the lower limit of the rated primary current is ≥ 10 mA, the rated power is 50 mVA, the rated frequency is 50... 400 Hz, and the internal resistance is 5... 8 Ω. The secondary overvoltage protection adopts P6KE6V8CP suppression diode with an accuracy level of 5. Rated continuous thermal current 100 A, rated short-time thermal current 14 kA/1 s, rated dynamic current 35 kA/30 ms. These parameters indicate that the WR series can measure both small residual currents and withstand high short-term fault current surges.

In terms of environmental adaptability, the equipment can withstand 15 g/11 ms impact, 40 g/6 ms collision, 1 g/10... 150 Hz working vibration, and 2 g/10... 150 Hz transportation vibration. Working temperature range -10...+50 ° C, storage temperature -40...+70 ° C, climate level 3K22. The connection adopts screw terminals, rigid/flexible conductors of 0.2... 4 mm ² or 0.2... 2.5 mm ², flexible wires with or without plastic sleeves of 0.25... 2.5 mm ², AWG 24... 12. When connected to the evaluator, single wire ≥ 0.75 mm ² can be used for 0... 1 m; twisted pair single wire ≥ 0.75 mm ² can be used for 0... 10 m; shielded cable ≥ 0.6 mm ² can be used for 0... 40 m. It is recommended to J-Y (ST) Y min. 2 × 0.6, and the shielding layer should be single ended with PE. These wiring requirements are very important to ensure signal integrity.

Installation specifications and key points for threading

The first principle when installing the WR series is: do not pass shielded cables through the measuring current transformer. The second principle is that PE conductors and low resistance conductor circuits shall not pass through transformers. The third principle is that all current carrying conductors must pass through in the correct direction. Specifically, for a three-phase system, L1, L2, L3, and N should pass through simultaneously; For single-phase systems, L and N should pass through simultaneously. P1 (K) side usually corresponds to the power supply side, and P2 (L) side corresponds to the load side, depending on the requirements of the evaluator. If the direction is reversed, the phase of the residual current and positioning current will reverse, affecting measurement and positioning.