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ACTAS P / L / C - Three product lines, one software!

06. July 2021, cstuden - Circuit breaker testing

When we talk about "P L C" at KoCoS, we don't mean the programmable logic controller but our various ACTAS test systems. But why does KoCoS offer three different ACTAS product lines?

Quite simply! KoCoS serves the entire mechanical switch testing market with its three different ACTAS product lines. Starting with fully automatic routine testing at the switchgear manufacturer, through the service technician to the test laboratory. The requirements of the various applications can only be optimally met with different devices.

 

Use of the ACTAS test systems

 

ACTAS Portable           Service Technician (manual testing)

 

ACTAS Laboratory       Test laboratories, production, development (semi-automatic testing)

 

ACTAS Cabinet            Test laboratories, production, development (fully automatic testing)

However, the situation is quite different when it comes to testing software, where an end-to-end solution is important:

With ACTAS 2.60, all tests can be performed with all ACTAS test systems. This is essential in order to be able to reuse tests and test results throughout the entire life of the switchgear. It is then possible to test a switch with ACTAS from the start of its development through to its use in the field, e.g. under using the same templates. For example, the test parameters and limit values developed in the laboratory with ACTAS L can be used directly during routine testing as part of the quality assurance process with ACTAS C. With ACTAS P, the service technician is then also able to access the original parameters during maintenance.

Almost all major switchgear manufacturers, test laboratories and also service technicians appreciate this and take advantage of the great ACTAS benefit of being able to use measuring instruments flexibly for the various applications and to fall back on existing data.

Any questions or additions to the topic? Then please use the comment function here on the blog or send an email to cstuden(at)kocos.com.

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Estimation of the maximum short-circuit current Ik_max of a transformer.

22. June 2021, estachorra - Engineering & Services

In practice, the value of the maximum short-circuit current "Isc_max" of a transformer is often needed. On the one hand, to be able to estimate the current carrying capacity of input circuits, such as in the KoCoS fault recorder system SHERLOG. It must also be taken into account that typical protection current transformers used in medium voltage can transmit currents up to 40 times higher than the rated current of the transformer in the event of a short circuit. On the other hand, a typical application is the plausibility check of the parameters of the high current stage of a transformer protection relay during the commissioning or repeat protection test, for example with our relay test system ARTES.

The following formulas are used to estimate the maximum short-circuit current "Ik_max" for three-phase medium-voltage transformers. The determined current value "Ik_max" is in practice somewhat higher than the real short-circuit current "Ik_max_real" which actually occurs. The estimation is therefore made to the "safe side".

The following equations 1 and 2 show that the estimation can be done for the primary as well as for the secondary side. When using equation 1 and equation 2, it should be noted that "usc" must be entered as a percentage in the equations for the relative short-circuit voltage.

If the rated current of the transformer is not explicitly known (for example, only “Srated_transformer” and “uk” are often specified in network calculations for transformers), the tailored quantity equation 3 can be used. Note: This estimation of the maximum short-circuit current applies only to three-phase medium-voltage transformers with a secondary voltage of Unom_sec = 400V. Also, when using equation 3, note that the relative short-circuit voltage "usc" in percent must be inserted into the equation.

When transformers are used, they are often referred to as "voltage-stiff" or "voltage-soft" transformers with regard to the behaviour of the secondary voltage during load changes. Equations 1 and 2 show that the maximum short-circuit current increases with decreasing "uk" (voltage-stiff) and the maximum short-circuit current decreases with increasing "usc" (voltage-soft). The short-circuit voltage “Vsc” and thus also the relative short-circuit voltage “usc” are a measure of the internal resistance of the transformer.

Voltage soft: When loaded, the output voltage of the transformer decreases. The output current hardly changes. The transformer is short-circuit proof (example: welding transformer).

Voltage stiff: Under load, the output voltage of the transformer hardly decreases. The output current increases. The transformer is not short-circuit proof.

As an aid to remembering the behaviour of the transformer's output voltage, a very hard and a soft cushion can be used. If the same amount of pressure is applied to a very hard and a soft pad, the hard pad is depressed significantly less than the soft pad. The depth of the indentation on the cushion is synonymous with the behaviour of the output voltage of the transformer.

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Inspection of tube geometries with LOTOS 3D measuring systems

17. June 2021, pzube - 3D measurement and inspection

Inspection of tube geometries with LOTOS 3D measuring systems

Precise inspection of various processing steps in tube manufacturing is gaining enormous importance. On the one hand, it is important to automate processes, on the other hand, it is indispensable for a cost-efficient production to detect rejects as early as possible.
If defects are only detected during the final inspection or even after delivery to the customer, they lead to extremely high costs.
The requirements for accuracy and fast, process-reliable inspection, up to 100% inspection of the components directly in production, are constantly increasing.

The LOTOS 3D measuring systems are used both for quality inspection of the tube pieces and for process control and defined alignment for the next processing steps.

Thereby LOTOS systems check for example:

  1. Geometries from cross-sectional contours through to free-form surfaces
  2. Positions and geometries of holes and laser cutouts
  3. Length, straightness, perpendicularity and flatness of the tube pieces
  4. Processing states of tube ends, such as chamfers or fillets of tube edges
  5. Correct alignment to a defined position based on geometric features
3D scan of a filleted tube edge
3D scan of a filleted tube edge
Geometry inspection of a tube
Geometry inspection of a tube
Checking the geometry of a laser cutout incl. its position on the part
Checking the geometry of a laser cutout incl. its position on the part
Inspection of chamfered tube edges
Inspection of chamfered tube edges
Inspection of filleted tube edges
Inspection of filleted tube edges
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Redispatch 2.0

07. June 2021, mjesinghausen - Power quality analysers , Digital fault recording

Redispatch 2.0

Electricity network operators are required by the Energy Industry Act to ensure the security and reliability of the electricity supply in their network.

Redispatch refers to interventions in the generation output of power plants in order to protect line sections of the electricity network from overload and avoid bottlenecks. If there is a threat of congestion, certain power plants are instructed to reduce their feed-in capacity. At the same time, other power plants must increase their feed-in capacity. This balance-neutral control creates a load flow that counteracts the bottleneck.

Due to the steady growth of renewable energies, whose feed-in capacity is also largely determined by the weather and is subject to strong fluctuations during the course of the day, grid operators have to carry out redispatch measures more and more frequently. 

Previously, redispatch was only carried out with conventional large-scale power plants of 10 MW or more.

With the new Redispatch 2.0, all generation plants with a generation capacity of 100 kW or more, as well as smaller plants that can already be remotely controlled by the grid operator, will also be included in this control process on a mandatory basis. This also includes many decentralized CHP, wind and photovoltaic plants. 

The aim is to increasingly use even more accurate forecast data for predictive grid control in order to ensure grid stability and avoid bottlenecks. In addition, decentralized EEG plants are often located closer to the bottleneck to be resolved and can therefore be deployed in a more targeted manner. This reduces the control services required from large power plants and helps to lower costs in the overall system.  

When Redispatch 2.0 comes into force on 01.10.2021, operators of affected generation plants will be obliged to regularly provide comprehensive data to the grid operator. This includes, among other things, the live measurement data of the plant, which the grid operator can use to determine the power reserve available to it on the basis of the average power value of the past 15 minutes and use it for redispatch. This data is also used to determine possible compensation payments. 

But it is not only the power data that is of interest here. The applicable technical connection rules for power generation plants in medium and high-voltage networks VDE-AR-N 4110 and VDE-AR-N 4120 additionally prescribe the monitoring of voltage quality according to EN 50160 Class A as well as the high-resolution recording of network disturbances.

The measuring systems of the EPPE and SHERLOG product lines fully meet the requirements. Permanent power quality measurements, transient disturbance recordings as well as real-time measurement data transmission and visualization are performed in parallel and independently on these systems.  

Voltages and currents are recorded with a temporal resolution of 200 kHz and a measurement deviation of maximum 0.05%. The resulting data is stored fail-safe in a 32 GB ring buffer and transmitted via cable or LTE/G5-based network connection or can be read out directly at the device via USB interface. The remote data transmission can be time or event controlled. Thus, for example, a detailed fault report including the fault type, fault duration, maximum values that occurred, fault impedance and fault location can be automatically generated by the associated Expert software just a few seconds after a fault occurs and sent to operations management, e.g. by e-mail. Voltage quality reports can also be generated automatically and stored as PDF reports. Real-time measurement data can be read out via MODBUS or IEC 61850, for example, and visualized on all common browsers and platforms via the integrated web server.

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