IDMT relay is inverse definite minimum time relay. It is one in which Time of operation is inversely proportional to magnitude of fault current near pickup value and becomes substantially constant slightly above the pickup value of the Relay.
- Canlculate IDMT Over Current Relay Setting (50/51)
- Calculate IDMT Over Current Relay Pick up setting.
- Calculate IDMT Over Current Relay PSM.
- Calculate IDMT Over Current Relay Time setting.
- Calculate Actual Operating time according to Various IES Curve.
- Calculate Low current Setting(I>).
- Calculate High Current Setting(I>>)
- Calculate Actual Operating Time of Relay(t>)
- Calculate Actual Operating Time of Relay(t>>)
- Calculate IDMT Earth Fault Relay Setting (50N/51N)
- Calculate IDMT Earth Fault Relay Pick up setting.
- Calculate IDMT Earth Fault Relay PSM
- Calculate IDMT Earth Fault Relay Time setting
- Calculate Actual Operating time according to Various IES Curve.
- Calculate Low current Setting(Ie>)
- Calculate High Current Setting(Ie>>)
- Calculate Actual Operating Time of Relay(te>)
- Calculate Actual Operating Time of Relay(te>>)
Inverse definite minimum time (IDMT) relays are commonly used for protecting electrical systems from overcurrent and earth faults. To set the parameters for an IDMT overcurrent and earth fault relay, you need to consider various factors such as the protection requirements, fault current levels, and coordination with other protective devices. Here's an overview of the process:
Determine the Relay Type: First, decide whether you need a relay for overcurrent protection, earth fault protection, or a combination of both. Overcurrent relays protect against excessive current in normal operation and short circuits, while earth fault relays specifically detect ground faults.
Select the Plug Setting Multiplier (PSM): The PSM is a ratio that determines when the relay will trip relative to the rated current. Higher PSM values provide more time before tripping, while lower values result in faster tripping. PSM is typically chosen based on system characteristics, such as cable impedance and fault conditions.
Time-Dial Setting: The time-dial setting is used to adjust the relay's time-current characteristic. This setting, usually represented as a time multiplier, allows you to fine-tune the tripping time. It's important to consider the coordination with downstream and upstream protective devices when selecting this setting.
Plug Setting (PS): The plug setting is calculated based on the relay's PSM and the desired tripping current. It's expressed as a multiple of the rated current. The formula to calculate PS is: PS = Rated Current / PSM.
Select the Time-Current Curve: Depending on the relay's characteristics and the desired protection, you need to choose the appropriate time-current curve. Common curve types include Normal Inverse (NI), Very Inverse (VI), Extremely Inverse (EI), and Long-Time Inverse (LI).
Coordinate with Other Protective Devices: Ensure that the IDMT relay settings are coordinated with other protective devices in the system. This coordination is essential to minimize the impact of false tripping and ensure that the fault is cleared by the most suitable protective device.
Earth Fault Sensitivity: For earth fault relays, set the sensitivity to detect ground faults. This sensitivity can be adjusted depending on the system's grounding configuration (e.g., solidly grounded, ungrounded, or impedance grounded).
Testing and Verification: After configuring the relay settings, it's crucial to test and verify their performance through simulation and real-world testing. This ensures that the relay operates as expected under fault conditions.
Documentation: Maintain detailed records of the relay settings, including PSM, time-dial settings, plug setting, and curve type, in the system documentation for future reference and maintenance.
Relay setting is a critical aspect of electrical protection, and it requires a deep understanding of the system, fault characteristics, and coordination with other protective devices. It's often performed by electrical engineers or specialists to ensure the reliable and efficient operation of the protective relay.
