Bliksembescherming voor kritische installaties

Over Nederland gemiddeld is de kans op blikseminslag Ca. 2 tot 4 per jaar per vierkante kilometer. De kans op schade door een directe inslag in een object is tamelijk klein. Veel laagbouw in steden wordt bijvoorbeeld nauwelijks voorzien van een bliksemafleider. Voor hoogbouw of afzonderlijk staande bebouwing is zo’n bescherming echter wel wenselijk. Een afleider biedt de bliksemstroom een pad om het gebouw naar de Aarde . Dit pad wordt primair ontworpen op een lage weerstand. Zo verlaagt men de dissipatie die vooral optreedt tij dens de langdurende volgstromen bij een inslag, en blijft de kans op brand klein

The importance of common mode currents in high-voltage substations

We measured in a substation the common mode (CM) curronts through secondary cables at the entry of a kiosk or a control room. Parameters of interest are the waveshape, the maximum dlldt, the amplitude and the frequency content. With these parameters and the biown transfer impedance of the cables one can test the adequacy of E7~iC measures to protect the electronic equipment. In addition, the measured parameters can be compared ~i6th calculated CM currents in substation

EMC, ook voor interne storingen

In situations with intense disturbances, where measurements are to be made continuously, a reliable and linear protection of electronic systems is essential. Such an EMC-approach turns out to be possible. A description consistent with Maxwell's laws is given, with emphasis on grounding. Many tests under difficult circumstances have shown the validity of the concept

Reliable protection of electronics against lightning: some practical applications

The classical lightning conductor, which must prevent fire, has to have a sufficiently small resistance. An analogous condition can be formulated for the new challenge: the protection of sensitive electronics against lightning. In this case, the so-called transfer impedance, which gives the interference voltages across a sensitive input per ampere lightning current, must be made small. The arguments for this approach are described. A theoretical description is available and practical experience has been built up over the years, also in high-voltage (HV) research and in power engineering measurements in the field. This approach was used to greatly improve the lightning protection of several installations: a marine radio station, the peripheral equipment of a nuclear power plant, and an electronic siren for a nationwide public warning system. Detailed investigations were requested by our contract partners, together with suggestions for economically acceptable improvements that could be carried out in reasonable time. Later, the correctness of the renovations had to be demonstrated. In the validation measurements, we injected currents into the installation or into relevant parts thereof. The current waveform was chosen fast enough so that inductive effects determined the current distribution. At present, lightning position and tracking system (LPATS) data on lightning strikes near the marine radio station and the nuclear power plant are available to verify the effectiveness of the protection. After our improvements no more damage was reporte

Toepassingen van D/I meetsystemen

IN POWER GRIDS VOLTAGES AND CURRENTS SHOULD BE RELIABLY MEASURED DURING OVERVOLTAGES, SWITCHING EVENTS AND FAULT SITUATIONS BUT ALSO DURING 50 Hz OPERATION. THE MEASURING SYSTEM WHICH LINKS THE POWER SYSTEM, FOR INSTANCE A SUBSTATION, TO THE DATA HANDLING, SHOULD CORRECTLY ADAPT THE SIGNALS TO THE MODERN ELECTRONICS. OTHER SPECIFICATIONS ARE THE SYSTEM’S EMC QUALITY, ITS BANDWIDTH, LINEARITY AND COST AND ITS APPLICABILITY IN OPEN AND CLOSED SUBSTATIONS. A COMPLETE SYSTEM IS DESCRIBED THAT EXCELLENTLY FITS ABOVE REQUIREMENTS. THE APPLIED DIFFERENTIATING/INTEGRATING PRINCIPLE IS SIMPLE, HAS A LARGE BANDWIDTH AND HIGH EMC QUALITY, AND CAN BE USED WITH LONG COAXIAL CABLES. GLASS FIBERS ARE NOT NEEDED. WE APPLY THE SYSTEM IN OUR HIGH-VOLTAGE WORK, FOR SUBSTATION MEASUREMENTS AND IN MANY THIRD PARTY EMC PROJECTS, OFTEN WITH RESPECT TO LIGHTNING PROTECTIO

Efficiency and reliability of a repetitive pulse source for continuous pulsed corona processes

Successful introduction of pulsed corona for industrial applications depends very much on the reliability of the high-voltage and pulsed power technology, as well as on the efficiency of energy transfer from the AC-mains to the corona discharge.\u3cbr/\u3eFurthermore adequate electromagnetic compatibility (EMC) should be achieved between high-voltage pulse source and surrounding equipment. A prototype of an industrial high-voltage pulse source which closely meets these demands has been developed

Three phase voltage measurements with simple open air sensors

A low cost, easy to install high-voltage measuring system is described for open air substations and overhead lines. Based on the Differentiating/Integrating (D/I) principle, three free-standing capacitive pickup electrodes are used to sense the three phase to ground voltages. Apart from the individual phase aimed at, each sensor also receives a parasitic contribution from the other two phases. After integration the sensor signals therefore have to be unscrambled to recompose the original phase voltages The system has a large bandwidth, is linear and has excellent Electro-Magnetic Compatibility (EMC) properties. With its low cost, simple installation and EMC quality, the system may be incorporated easily into various applications like e.g. monitoring and line protection