Power Distribution and Monitoring System H-NETClamp Type Current Sensor (CT)

Protection function for opening of the secondary side

If the secondary side of the CT is opened due to a broken wire, etc., a voltage of several kV is generated on the secondary side, which may damage the CT or cause an electric shock.
With the 10 mA Output Series, the lead may cover long distances, which increases the risk of secondary-side opening, such as a break in the wiring. However, a protection function is provided to keep the voltage at the time of opening of the secondary side down to 6.5 V, ensuring safety in the unlikely event of opening.

Maximum distance

The 10 mA Output Series can be used with the secondary circuit voltage of up to 6.5 V, which allows the lead to be as long as up to 300 m.

Precautions

This is a dedicated product for the H-NET unit and cannot be used with other AC meters, etc.

CT selection

• For new installations, select a general-purpose CT (5 A Output Series) because there are no installation restrictions.
  For the H-NET units (power monitoring unit and electrical energy calculation unit) to be combined with the CT, select 5 A input products.
• For existing equipment, select a clamp CT that can be installed without disconnecting the wires.
• Clamp CTs for H-NET are available in the 5 A and 10 mA Output Series, with the 10 mA Output Series, which features easy installation and a long maximum distance, being widely used.
  For the H-NET units (power monitoring unit and electrical energy calculation unit) to be combined with the CT, select 10 mA input products.
• Determine the primary current rating value after due consideration of the capacity of the circuit breaker and the actual load current.
  In addition, select a product with an inner diameter appropriate for the size of the cable to be mounted.

Selection by load current

• Measurement errors and measurement limits depend on the rated current value of the CT. Select a CT with a rated value close to the operating current value.
• If the rated value of the CT is much larger than the operating current, both the current indication and the electrical energy count may be treated as “0” due to the measurement limit of the unit.

Measurement limit

	Current (% with reference to the secondary current rating of CT)	Electricity (Value with reference to the secondary rating of CT and VT)
Power monitoring unit	2%	10W
Electrical energy calculation unit	2% (R, T)	10W

Determine the primary current rating value so that the load current is at least 10%.

Selection by CV cable size

○: Acceptable, △: May not be acceptable depending on cable bending conditions, ×: Not acceptable