EUROLAB, with its state-of-the-art accredited laboratories and expert team, provides precise and fast testing services within the scope of IEC EN 60255-151 testing. IEC EN 60255-151 specifies minimum requirements for over/undercurrent relays. It includes properties of protection function, measurement properties and time delay properties. It identifies the factors affecting accuracy under steady state conditions and performance characteristics during dynamic conditions.
If any binary input signals (externally or internally driven) are used, their effect on the protection function must be clearly defined in the functional logic diagram. Additional textual description may also be provided if it could further clarify the functionality and intended uses of the input signals.
The relationship between operating time and characteristic quantity can be expressed by means of a characteristic curve. The shape of this curve should be declared by the manufacturer by an equation (preferred) or graphical means.
Relay reset characteristics must be defined by the manufacturer to allow users to determine the behavior of the relay in the event of repetitive intermittent faults or faults that can occur in rapid succession. Different reset characteristics can be used depending on the settings on the relay and whether the element completes its operation.
The tests described in this article are for type tests. These tests should be designed to apply all aspects of the over/undercurrent protection relay hardware and firmware (if applicable). This means that the current injection must have an equivalent signal at the relay interface, either directly to the conventional CT input terminals, or at the appropriate interface. Similarly, action should be taken from output contacts or equivalent signals at a suitable interface whenever possible.
If for some reason it is not possible to measure results from signal input to output, the point of application of the characteristic quantity and the signal interface used for measurement must be declared by the manufacturer. A current transformer ratio can be selected to perform tests on relays where the settings are at primary values. To determine the accuracy of the relay under steady-state conditions, the injected characteristic quantity must be a sinusoid of the rated frequency and its magnitude must be changed according to the test requirements.
Depending on the technology of the relay under test, it may be possible to reduce the number of test points in line with the limited range and step size of the available settings. However, if the listed test points or the exact value cannot be reached, the closest available setting should be used.
EUROLAB assists manufacturers with IEC EN 60255-151 test compliance. Our test experts, with their professional working mission and principles, provide you, our manufacturers and suppliers, the best service and controlled testing process in our laboratories. Thanks to these services, businesses receive more effective, high-performance and quality testing services and provide safe, fast and uninterrupted service to their customers.
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