BENDER IRDH575 Insulation Monitoring



BENDER IRDH575 A-ISOMETER Insulation Monitoring and Grounding Fault Location Controller Technical Guide

Non grounded (floating) AC/DC systems are widely used in industrial power distribution, ships, mines, rail transit, photovoltaics, energy storage, and variable frequency drive systems due to their advantages in power supply continuity. But once insulation degradation or grounding fault occurs in the floating ground system, if it cannot be located in time, it may evolve into phase to phase short circuit, equipment damage, or even fire. The BENDER IRDH575 series A-ISOMETER is a digital ground fault monitor and ground detection controller designed for this type of scenario. It can not only monitor the insulation resistance of the system to ground, but also serve as the control core of the grounding fault location system, cooperating with positioning devices such as EDS460 and EDS461 to achieve a complete closed-loop from alarm to branch positioning.

Product positioning and core capabilities

The IRDH575 series is suitable for 3 (N) AC, AC/DC, and DC ungrounded systems. Depending on the model, the nominal system voltage covers 20... 575 V or 340... 760 V, with a response range of up to 1 k Ω... 10 M Ω. The equipment determines grounding faults by measuring the system's insulation resistance to ground and can detect insulation defects before leakage current becomes apparent. For systems containing a large number of power electronic components such as rectifiers, frequency converters, and PLC control circuits, IRDH575 can still maintain stable monitoring.

Its core capabilities include: universal ungrounded system monitoring, dual independent alarm relays, warning and main alarm grading, self-monitoring function, system fault alarm, internal/external testing and reset, backlit LCD display, RS-485/BMS communication, 0/4... 20 mA analog output, 99 time stamp alarm recording, system disconnection function, and a grounding fault location system that can be extended to 1080 circuits.

Grounding fault detection principle

IRDH575 continuously measures the insulation resistance between an ungrounded system and ground. When the insulation resistance is lower than the set response value, the alarm relay will activate and the panel alarm LED will light up. Two alarm contacts can be set as warning and main warning respectively, making it easier for operation and maintenance personnel to handle them in a graded manner. The measured values can be displayed on the LCD or connected to external instruments or upper control systems through analog outputs.

The device supports both locked and unlocked modes. In non locked mode, the alarm will automatically clear after the ground fault disappears; In locked mode, it must be manually reset or powered off before resetting. Testing and resetting can be completed through panel buttons or remotely operated through external buttons. The INFO menu can display key information such as current leakage capacitance and device settings. IRDH575 continuously monitors the grounding and line connections of the equipment to ensure the reliability of its measurement circuit.

Grounding fault location system

When IRDH575 detects a ground fault, it can automatically activate the EDS ground fault location system or be set to manually start. Each EDS channel is connected to a branch circuit, and IRDH575 emits a pulse test signal. The signal returns to IRDH575 through the EDS channel along the fault branch, thereby displaying the fault channel simultaneously on both IRDH575 and the EDS device. The test current is adjustable, with typical values of 1, 2.5, 10, 25, and 50 mA, and pulse/interval of 2 s/4 s. For complex systems, the EDS30 portable locator can also be selected to track the fault source along the pulse signal.

Outstanding system scalability: One IRDH575 can interconnect up to 90 EDS46... devices, with each EDS monitoring 12 independent channels and a theoretical maximum positioning loop of 1080. Each isolation system only needs to be equipped with one IRDH575 as the detection and positioning control core.

Human machine interface and wiring points

The front panel includes buttons such as INFO, ESC, TEST, up-down direction, RESET, MENU, Enter, etc. LED indicators include: Alarm 1, Alarm 2, EDS positioning activation, EDS alarm, and system failure. LCD displays real-time insulation resistance k Ω and can display EDS address, channel, detection signal strength, AUTO/manual mode, test current pulse polarity, and device status text.

Backplane wiring includes: system connections L1/L2/L3, power supply A1/A2, equipment grounding KE, RS-485 A/B, alarm relays K1/K2/K3, external testing/reset, STANDBY contacts, etc. The power supply voltage can be AC 88... 264 V/DC 77... 286 V, or DC 19.2... 72 V depending on the model. It is recommended to use 6A fuses for power supply, and two fuses are required for power supply in IT systems. The RS-485 terminal resistor is 120 Ω and can be connected to the BMS bus through the micro switch S1.

Key technical parameters and selection

IRDH575 complies with IEC 60664-1 insulation coordination, rated insulation voltage AC 800 V, rated impulse voltage/pollution level 8 kV/3. The voltage of the B1 type system is AC/DC 20... 575 V, and the B2 type is 3 (N) AC 340... 760 V, DC 340... 575 V. The rated frequency is 50... 460 Hz, and when it is below 50 Hz, the characteristic curve should be referred to.

The measurement circuit measures voltage ≤ 40 V, current ≤ 220 μ A, and internal DC resistance ≥ 180 k Ω. It is allowed for external DC voltage B1 ≤ 810 V and B2 ≤ 1060 V. System leakage capacitance ≤ 150 (500) μ F. The response value is 1 k Ω... 10 M Ω, and the relative error is 0%...+20% within the range of 10 k Ω... 10 M Ω. The range of 1 k Ω... 10 k Ω is+2 k Ω. The lag is 25%+2 k Ω.

Display as backlit LCD, 4 × 16 characters, character height 5 mm. Analog output 0/4... 20 mA, load ≤ 500 Ω. The maximum cable length of RS-485/BMS is 1200 meters, and it is recommended to use shielded cable J-Y (ST) Y 2 × 0.6. The switch components consist of three sets of SPDT contacts: K1 alarm 1, K2 alarm 2, K3 equipment fault/EDS alarm. K1 and K2 can be selected as normally excited or de excited, and are factory de excited; K3 is normally excited. Contact rated AC 250 V/DC 300 V, connect 5 A, disconnect 2 A (AC 230 V, cos φ=0.4... 0.2 A; DC 220 V, L/R=0.04 s). The electrical lifespan is 12000 cycles.

In terms of selection: IRDH575B1-427 is AC/DC 20... 575 V, powered by DC 19.2... 72 V; IRDH575B1-435 is 3 (N) AC/DC 20... 575 V, powered by AC 88... 264 V/DC 77... 286 V; IRDH575B1-4227 is 3 (N) AC/DC 20... 150 V, powered by DC 19.2... 72 V; IRDH575B1-4235 is AC/DC 20... 150 V, powered by AC 88... 264 V/DC 77... 286 V; IRDH575B2-435 is 3 (N) AC 340... 760 V, DC 340... 575 V, powered by AC 88... 264 V/DC 77... 286 V. Some models measure a voltage of 10 V. When selecting, attention should be paid to the system voltage, power supply method, and measurement voltage requirements.

Debugging and common troubleshooting

When debugging IRDH575, the system voltage, power supply voltage, fuses, grounding connections, and RS-485 terminals should be confirmed first. Set response value, alarm mode, locked/unlocked, analog output type, and EDS mode. If EDS positioning is used, the EDS address, channel, and test current need to be set, and the direction and wiring of the current transformer need to be confirmed.

Common problem one: Frequent insulation alarm. Check whether the actual insulation resistance and response value are too small, whether the system leakage capacitance is too large, whether the frequency converter filter capacitance is affected, and whether the wiring terminals are damp. The INFO menu allows you to view the leakage capacitance and adjust the response value or troubleshoot the load in batches if necessary.

Common problem 2: System malfunction alarm. Focus on checking the grounding of KE equipment, L1/L2/L3 wiring, power supply insurance, and self-monitoring circuit. If the device is poorly grounded, IRDH575 may report a system malfunction.

Common problem three: EDS is not located. Confirm whether the EDS LED is activated, whether the AUTO mode is turned on, whether the EDS address and channel are correct, whether the test current is sufficient, and whether the transformer is installed in the correct branch. If the pulse signal is weak, the test current can be increased, but it must be ensured that it does not exceed the allowable value of the system.

Common problem four: RS-485 communication abnormality. Check the polarity of A/B, whether the terminal resistance S1 is set to ON at the end of the bus, whether the shielding layer is single ended grounded, and whether the cable length exceeds 1200 m. Ethernet, MODBUS, or PROFIBUS can be connected through a protocol converter.

Common problem five: Analog output deviation. Confirm the 0... 20 mA or 4... 20 mA settings, whether the load is ≤ 500 Ω, and whether the PLC analog input configuration matches.

Application suggestions

IRDH575 is suitable for floating ground systems that require continuous power supply and high reliability. For multi branch systems, it is recommended to adopt the architecture of IRDH575+EDS460/EDS461+W series current transformers. The communication main circuit can use EDS460, and the PLC or DC control circuit can use EDS461. Each isolation system is independently configured with an IRDH575 to avoid cross system interference. For coupled ungrounded systems, STANDBY contacts can be used to achieve coordinated operation of multiple A-ISOMETERs.

In scenarios such as ships, mines, metallurgy, chemicals, data centers, energy storage, and rail transit, the early warning and positioning capabilities of IRDH575 can significantly shorten troubleshooting time and reduce unplanned downtime. Its RS-485, analog output, and relay interfaces make it easy to connect to existing SCADA, PLC, or BMS systems.