IEC EN 60909-3 Short Circuit Currents in Three-Phase AC Systems - Part 3: Currents During Two Separate Simultaneous Phase-to-Earth Short Circuits and Partial Short-Circuit Currents Flowing From Ground

EUROLAB, with its state-of-the-art accredited laboratories and expert team, provides precise and fast testing services within the scope of IEC EN 60909-3 testing. This standard specifies procedures for calculating possible short-circuit currents with an unbalanced short-circuit in high-voltage three-phase AC systems operating at a rated frequency of 50 Hz or 60 Hz.

The currents calculated by these procedures are used when determining the induced voltages or touch or step voltages and rise of ground potential at a station (power station or substation) and towers of overhead lines. Procedures for calculating the reduction coefficients of overhead lines with one or two earth wires are given.

The standard does not cover:

• Intentionally generated short-circuit currents under controlled conditions, such as in short-circuit test stations;
• Short-circuit currents in electrical installations on ships or aircraft;
• Single line-to-earth fault currents in isolated or resonant earthed systems.

The purpose of this standard is to establish practical and concise procedures for the calculation of line-to-line short-circuit currents during two separate simultaneous line-to-earth short circuits and partial short-circuit currents along the ground, ground wires of overhead lines. and sheaths or shields of cables with sufficient accuracy leading to conservative results. For this purpose, short-circuit currents are determined by setting all other voltage sources to zero considering an equivalent voltage source at the short-circuit location. When calculating the short-circuit currents at the short-circuit location, the resistances of the grounding networks at the stations or the basic resistances of the overhead line towers are neglected.

The calculation of short-circuit currents based on the rated data of the electrical equipment and the topological arrangement of the system has the advantage of being possible for both existing systems and systems in the planning stage. The procedure is suitable for determination by manual methods or by digital calculation. This does not exclude the use of special methods, such as the superposition method, which are adjusted to certain conditions, if at least they give the same precision.

EUROLAB assists manufacturers with IEC EN 60909-3 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.