The massive expansion of renewable energy systems has led to changes in the grid situation. For example, an enormous number of frequency converter systems are now feeding into the energy grid, which ultimately increases the requirements for flexible and secure grid monitoring. According to Matthias Schagginger, Senior Manager Product Line Management at Austrian automation technology provider Bachmann Electronic, this poses challenges for manufacturers of energy generation systems, among others: While they can rely on cost-efficient PLC technology for system control, they have so far had to use dedicated, decentralized units from classic energy technology for highly dynamic grid measurement or to ensure supply quality and for fault analysis. This is because current module designs with a focus on energy data acquisition for the low-voltage range or for laboratory applications are not suitable for professional use on generation systems or transmission components.

Against this background, the idea of bringing the previously separate worlds of energy and automation technology closer together matured in Feldkirch. The result is the new GMP232/x, a grid measurement and monitoring module embedded in Bachmann's M1 automation system. This can be placed anywhere within the modular control system on main or decentralized substations. "All measurement, calculation and status information from the module is thus available for user programs on the CPU. This enables both the combination of system control and grid technology as well as the realization of freely programmable and highly flexible grid acquisition points in a compact modular unit," explains Matthias Schagginger.

Voltage measurement with the new module can be carried out directly up to 690 V, and an interface variant for transformers up to 120 V nominal value is also planned. The usual transformers for 1 A or 5 A are used for current measurement. The 40 parameterizable monitoring functions of the GMP232/x modules make it easy to set up the desired combination for mains and system intrinsic protection.

Numerous setting options for the source variables (e.g. true RMS or fundamental oscillation data, reference to nominal value or current cosystem) as well as time-limited trip blocking (e.g. in the event of undervoltage or strong asymmetry) also make handling easier. Last but not least, relay outputs integrated in the module enable the direct switching of two tripping circuits, independently of the rest of the PLC system.

When asked what sets the GMP232/x module family apart from previous solutions on the market, Schagginger points to the measuring range and frequency accuracy, among other things: "The true detection range of 1.7 or 3.4 times the rated voltage - based on 690 or 100 V respectively - and three or four times the rated current is very generous for the GMP and dimensioned for professional use. This means that the measured values during a mains fault are not only detected as 'out of range', but also mapped in terms of amplitude and shape. And this with an accuracy in terms of voltage and current of 0.1 % in relation to the nominal value." Typical competitive data in the control-related environment would be 1.2 to a maximum of 1.5 × Un or In, with an accuracy of between around 0.6 and 0.75 % in relation to the nominal value.

In terms of frequency measurement accuracy, the Bachmann solution is 1 mHz. This value is essential if generating units are to be operated in a controlled manner. In contrast, the frequency accuracy of conventional standard products is between 10 and 80 mHz. "This is no longer sufficient for current North American grid codes and will soon no longer be tolerated anywhere in Europe either," Schagginger points out.

Data recorder included

A powerful real-time data recorder is also integrated into the GMP232/x directly at the point where the data is generated. When protection is triggered, this automatically records the time histories of desired network variables with a resolution of up to 10 kHz. The pre-trigger function also makes it possible to record the time history of a fault. Recordings can also be triggered manually by a user or automatically via a PLC program.

The modules can also perform internal data aggregation so as not to burden higher-level systems such as control stations and central data acquisition with enormous amounts of data. In addition to the highly dynamic online values, average, minimum and maximum values are therefore also available via adjustable intervals.

Matthias Schagginger sees a particular strength of the control-integrated network technology not least in its comprehensive networking capability. All common telecontrol protocols such as IEC 61850, IEC 61400-25, IEC 60870-5-104, -103, -101, DNP3 or Modbus can be set up via the CPU modules and their interfaces. Ethernet and fieldbus communication in accordance with Profibus, Profinet, Ethercat, CAN or Devicenet can also be used to transfer network data. If only discrete signal interfaces such as 4 to 20 mA, ±10 V or proprietary serial communication are possible, the corresponding modules can simply be added.

In total, the GMP family comprises eight module types, which differ in the nominal values of the electrical interfaces (120 V/1 A, 690 V/1 A, 120 V/5 A, 690 V/5 A) and in terms of the environmental specification - i.e. standard versus condensation-proof 'ColdClimate' variant. Bachmann clearly sees the main application scenarios for the modules in generators (wind, hydropower, gensets, CHP) and transmission grid components (transformers, switches, compensation stations). The focus is also on applications for large electrical drives, for example in ships, but also in industrial plants.