Schneider Electric - Masterpact MTZ
Masterpact MTZ - Micrologic X - Circuit Breakers - Metering
Standard IEC/EN 61557-12: “Electrical safety in low voltage distribution systems up to 1000 V a.c. and 1500 V d.c. - Equipment for testing, measuring or monitoring of protective measures - Part 12: Performance measuring and monitoring devices (PMD)” covers both devices with external sensors, such as current or voltage transformers and standalone power meter and devices with embedded sensors like circuit breakers.
The introduction to this Standard is quite interesting, and makes the reader understand the importance of metering in today’s world: “As a complement to protection measures, it becomes more and more necessary to measure different electrical parameters, in order to monitor the required performances in energy distribution systems due to:
- Installation standards evolutions, for instance over current detection, is a new requirement for the neutral conductor due to harmonic content
- Technological evolutions (electronic loads, electronic measuring methods, etc)
- End-users needs (cost saving, compliance with aspects of building regulations, etc)
- Safety and continuity of service
- Sustainable development requirements where energy measurement, for instance, is recognised as an essential element of energy management, part of the overall drive to reduce carbon emissions and to improve the commercial efficiency of manufacturing, commercial organisations and public service
Masterpact MTZ equipped with Micrologic X and its own embedded sensors is a Class 1 full chain measurement device for active power and energy metering according to IEC/EN 61557-12.
The benefit of avoiding uncertainty and variation due to external sensors and wiring is one of the key factors that helped Masterpact MTZ in reaching this exceptional result.
In fact, IEC/EN 61557-12 standard defines three levels of uncertainty: intrinsic uncertainty, operating uncertainty and overall system uncertainty, that need to be checked to ensure accuracy class. The uncertainty is the estimated amount or percentage by which a measured value may differ from the true value.
Intrinsic Uncertainty Under Reference Condition
IEC/EN 61557-12 definition states that: “Intrinsic uncertainty is uncertainty of a measuring instrument when used under reference conditions”.
For Masterpact MTZ with Micrologic X, the main influence quantities are the current and the power factor.
The effect of all other influence quantities are less significant.
IEC/EN 61557-12 definition states that: “Operating uncertainty is uncertainty under the rated operating conditions”.
For Masterpact MTZ with Micrologic X, the main influence quantity is the temperature T°; Masterpact MTZ is designed to carry high current and so the self heating combined with the ambient temperature induces a wide range of operating temperature.
In Masterpact MTZ, the measurement has been designed to offer high stability within this range of temperatures.
Overall System Uncertainty
IEC/EN 61557-12 definition states that: “Overall system uncertainty is uncertainty including the instrumental uncertainty of several separated instruments, external sensors, external wiring between devices, etc. under the rated operating conditions”.
For Masterpact MTZ, the overall system uncertainty is non-existent thanks to its design with the embedded sensors.
Additional Disturbances: Behaviour Under High Harmonics
Thanks to other functions such as protection functions, Masterpact MTZ with Micrologic X offers by design a high level of immunity to disturbances.
Operating uncertainty is very low, ensuring a Class 1 in a wide range of operating conditions.
One Application: Compliance with IEC 60364-8-1 Clause 188.8.131.52 Requirement
IEC 60364-8-1 provides requirements and recommendations for the design, erection and verification of low voltage electrical installations including local production and storage of energy for optimising the overall efficient use of electricity.
It introduces recommendations for the design of an electrical installation within the framework of an energy efficiency management approach in order to get the lowest electrical energy consumption and the most acceptable energy availability. It also specifies the accuracies of the measuring instruments involved in the functions of energy management such as:
- Energy usage analysis & optimisation
- Contract optimisation
- Cost allocation
- Efficiency assessment
- Energy usage trends assessment
Masterpact MTZ with Micrologic X complies with the requirements of IEC 60364-8-1 dedicated to the optimisation of energy efficiency. It provides a range of measurements with accuracies required for complex energy efficiency approaches.
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