Date: 9th January 2008
Add-on earth leakage protection for MCCBs and MCBs
A new range of earth leakage relays and current transformers has been introduced by Eaton for use with moulded-case circuit-breakers and miniature circuit-breakers in three-phase and single phase applications. A unit with adjustable sensitivity and time delay facilities offers particular flexibility to specifiers and installers.
The earth-leakage relays are DIN rail mounted and operate in conjunction with core-balance current transformers. They control the circuit-breaker operation through a shunt trip or undervoltage release. Operational status is indicated by green and red LEDs which indicate not only whether the mains is on and the breaker has tripped but also whether there is an earth leakage current flowing which is insufficient to trip the device. Leakage currents of 25 50%, 50-75% or 75-100% of the trip setting are indicated.
The adjustable relay is only 36mm (two modules) wide. It offers seven different sensitivity settings from 30mA to 5A, and seven delay settings from instantaneous (0.02s) to 5s. The cover can be sealed to prevent tampering with the setting but the test and reset functions can be operated without breaking the seal. Two fixed trip relays are also included in the range covering two of the most popular requirements; these have 30mA and 300mA trip ratings and instantaneous operation. All units are designed and tested to IEC 61008-1.
The current transformers are available in sizes and shapes to cover a wide range of cable ratings and sizes. Ring-shaped units are offered in seven sizes with internal diameters from 20mm to 210mm and units with rectangular apertures are available in four sizes up to 200 x 500mm.
In addition to general applications, the new earth leakage relays will be particularly suited to applications in panelboards where the configuration can make it difficult to fit an MCCB with integral earth leakage protection or where a clip-on earth leakage module is fitted to the base of the MCCB. The rail-mounted earth leakage relays can be installed elsewhere in the panelboard or in a separate enclosure alongside. Similarly the CTs can be installed in a convenient location within the panelboard or in an adjacent cable box.
The new earth leakage relays join Eaton's extensive range of circuit protection and control devices. These include MCBs with a short-circuit breaking capacity of 15kA as well as the more conventional 6kA and 10kA devices. The range of RCCBs and RCBOs includes a unique RCBO with a field-fittable RCD 'pod' that allows numerous different combinations of overcurrent rating and sensitivity to be achieved in a single 18mm module. Eaton's modern Series G range of moulded-case circuit-breakers is a truly global design, independently tested by KEMA to International standards.
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