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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.

A look inside the switchgear chamber "Dynamic Timing" and "Dynamic Resistance

In contrast to evaluation via a simple binary signal, as is the case with high-frequency measurement methods, the use of switchgear test systems ACTAS in combination with resistance measuring devices PROMET allows a well-founded diagnosis of breaker units throughout the entire switching process. The result of the measurement is displayed in the form of a curve in which all events of a switching operation can be seen in detail. An exact assessment of the start of movement and end position of the contacts is thus made possible, even time differences between the movements of the main and resistor contacts become visible.

Evaluation of the breaker unit by means of contact resistance analysis

Regular measurements of the static and dynamic contact resistance allow precise statements to be made about the condition of the entire contact system. Necessary maintenance work can thus be detected at an early stage and downtimes prevented. With the PROMET SE resistance measuring device, contact resistance measurements can be carried out on up to 12 or more interrupters and directly integrated into the overall test sequence. The test current can be set up to a maximum of 200 A. Even very small resistances in the single-digit microohm range can be measured with extremely high accuracy. The measured values are included in the evaluation of the test and output in the test report.

A high contact resistance within a switching device leads to a high power loss, combined with thermal stress and possible destruction of the switching device. Faults, such as high contact resistance due to defective connections, can be detected by measuring the static contact resistance. With the dynamic contact resistance measurement, the resistance curve is determined during a switching operation that can be defined as desired. The measurement allows, for example, conclusions to be drawn about the length and condition of arcing contacts in high-voltage switches.

 

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 .

Is it possible to perform a switching time measurement on a medium voltage system encapsulated in SF6 gas?

KoCoS offers a measuring method using the ACTAS switchgear test systems and external sensors which enables this type of system to be tested at a reasonable cost. As the system does not need to be isolated, the measurement procedure is even less time consuming than testing a non-gas-insulated medium-voltage switchgear using the conventional measurement procedures.

The VDS (Voltage Detection System) installed in the systems is used to measure the switching times. These are capacitive measuring points for voltage indicators or integrated capacitive voltage indicators according to VDE 0682-415 or IEC 61243-5. If no voltage transformers are installed, these measuring points are the only and safe way to establish a connection to the main contacts of the circuit breakers.

The capacitive measuring points can be connected directly to the analog measuring inputs of the ACTAS test system provided for this purpose without interposing additional measuring components. The capacitive measuring points are used to measure the three-phase sine wave of the voltages. If the circuit breaker is switched via the control room, the voltage drop is displayed on the ACTAS test system. However, in order to be able to determine a switching time, current clamps are used and attached to the open and close coils. External trigger signals that can be set in the test system can be used to initiate the recording of the measured values and the corresponding evaluation. External triggers can be set in ACTAS to any signals, regardless of whether they are individual binary or analog signals or signal groups.

The evaluation of the switching time in ACTAS is fully automatic; there is no need to set a cursor to manually evaluate the switching times and enter values manually.

What advantage do FIRST TRIP measurements offer?

As an online test, using the first-trip measurement method with ACTAS has some advantages over offline testing. From an economic point of view, the amount of time that can be saved is particularly relevant, as the disconnection and isolation of the breaker from other equipment is completely eliminated. In addition, there are also savings with regard to maintenance costs and resources if no defects are detected during the online measurement as this may make it unnecessary to carry out a test in offline mode.

  • No need to disconnect the circuit breaker
  • No need to disconnect control circuits
  • Savings in measurement time and resources
  • Breaker sticking/delay can be detected during the first switching operation
  • It may be possible to do without a complex offline test
  • Tests are possible under real conditions
  • No long downtimes for the components to be tested

Using ACTAS, first trip measurements can be performed on three phases. For connection to secondary current transformers, up to nine external analog sensors, such as non-contact DC or AC clamps, can be connected to the test system simultaneously and recorded. Up to three direct voltage measurement channels are available for voltage transformers. The measuring equipment and sensors are mounted while the breaker is in operation. Usually AC/DC current clamps are used which are mounted on the secondary side of the current transformers and on the operating coils. The operating times can be evaluated via the signals recorded accordingly and the characteristic of the coil current can give an indication of the status of the components of the switchgear.

Is it possible to perform FIRST TRIP measurements with ACTAS Px60?


As a component part of the power supply system, a circuit breaker functions primarily as a pure conductor within the network and the only requirement it initially has to fulfil is that its transfer resistance be as low as possible. And this situation often persists for years at a time. As long as no fault occurs, there is no need for the circuit breaker to operate. This is very much in the interests of the network operator, but it poses a considerable challenge to the technology of the breaker because as soon as a fault occurs, the breaker has to interrupt a high fault current within a few milliseconds in accordance with its specifications. This is not always achieved, one of the reasons for this often being inadequate maintenance, and it can be that during the course of the first switching operation the circuit breaker does not open within the time specified by the manufacturer.

One of the causes for this is friction which is created by deposits such as hardened grease or by environmental influences. The problem is usually solved by the first switching operation, as this loosens indurations and deposits. If this is not the case and the problem persists over a number of switching operations, it can lead to serious damage to the breaker itself and to the power network too, of course.

This makes it all the more important to service and test switchgear in accordance with the specified cycles. By measuring the operating times, conclusions can be drawn as to the state of the contact system, and the first trip is, of course, particularly significant. With conventional (offline) measuring methods, however, the breaker is disconnected and earthed before the test and this requires that an initial switching operation be carried out before the measuring equipment is connected.

This makes it impossible to draw conclusions about the behaviour of the breaker during the first trip. This is just one of the reasons why the demand for testing circuitbreakers “online“, i.e. without disconnecting them beforehand, is increasing worldwide. Another reason is that operating and maintenance budgets are constantly shrinking.

In addition, the demands placed on modern testing technology are increasing, using it flexibly and in a way that saves time is a must nowadays. KoCoS Messtechnik AG meets these requirements with its ACTAS Px60 switchgear test systems.

This makes it impossible to draw conclusions about the behaviour of the breaker during the first trip. This is just one of the reasons why the demand for testing circuitbreakers “online“, i.e. without disconnecting them beforehand, is increasing worldwide. Another reason is that operating and maintenance budgets are constantly shrinking.

In addition, the demands placed on modern testing technology are increasing, using it flexibly and in a way that saves time is a must nowadays. KoCoS Messtechnik AG meets these requirements with its ACTAS Px60 switchgear test systems.

GIS system with earthing on both sides, is it also possible to measure the switching times?

In outdoor switchgear systems (AIS), measurement with ground on both sides is generally not a major problem, simply because the typical ground resistance is much higher than the main contact resistance. KoCoS uses "Dynamic Timing" to combine the ACTAS switchgear test system with PROMET resistance meters.

The standards DIN VDE0105-100 and EN50110-1 clearly state that a GIS system must be measured with ground on both sides.

The problem, which is particularly relevant for GIS, is the very low ground resistance resulting from the encapsulation of the entire switchgear in a metal housing. It often can be that the ground and housing resistance is lower than the main contact resistance. This makes it difficult to carry out a condition assessment of the switchgear using standard measuring equipment.

For testing GIS systems grounded on both sides, the Dynamic Timing method cannot be used in the same manner as used with AIS testing grounded on both sides. It is not possible to measure the correct switching time of the circuit breaker integrated in the GIS.

The components installed in GIS like current transformers, cause measurement delays. Depending on the switching sequence, the result will contain correspondingly faster switching times when tripping or slower switching times when closing.

KoCoS uses the “GIS Timing” method to measure correct switching times. For this measuring method, the GIS must have at least one insulated ground lead to the outside. Again, PROMET resistance meters are used which generate current outputs of up to 600 A depending on the version. The resistance measuring devices are controlled by ACTAS. The resistance measuring devices are only used as current sources and not as actual measuring instruments.

In order to obtain measured values, in addition to the resistance meters and ACTAS, current sensors specifically developed for KoCoS are used. They are flexible Rogowski coils which can be attached to the insulated ground. The current curves measured during the switching operation on the insulated ground can be used to determine the switching times for opening and closing during the various switching sequences of the circuit-breaker.

This “GIS Timing” method has a great safety advantage and still offers the possibility of evaluating the GIS systems by means of measurement results and correspondingly recorded measurement signals.

Timing measurements of AIS and GIS switchgear, what are the differences?

GIS high-voltage switchgears are located at many nodes in our voltage network, such as three-phase or single-phase encapsulated switchgear panels. High-voltage switchgears consist of several components and can be designed differently depending on the required function. They contain components such as current transformers, disconnectors, ground switches, circuit breakers, etc. Compared to air insulated switchgear (AIS), they offer a number of advantages, including smaller space requirement, higher personnel safety, a longer service life, and higher reliability. Disadvantages compared to AIS are evident in terms of maintenance, as individual components are very difficult to access. Measurements, such as those of circuit-breaker operating times and resistance of the circuit-breaker interrupter units, are rather difficult to carry out, since the basic requirement is that in high-voltage installations, all the parts being worked on must be grounded.

In outdoor switchgear systems (AIS), measurement with ground on both sides is generally not a major problem, simply because the typical ground resistance is much higher than the main contact resistance. KoCoS uses "Dynamic Timing" to combine the ACTAS switchgear test system with PROMET resistance meters.

The standards DIN VDE0105-100 and EN50110-1 clearly state that a GIS system must be measured with ground on both sides. The problem, which is particularly relevant for GIS, is the very low ground resistance resulting from the encapsulation of the entire switchgear in a metal housing. It often can be that the ground and housing resistance is lower than the main contact resistance. This makes it difficult to carry out a condition assessment of the switchgear using standard measuring equipment.