CIGRE in the Netherlands
In the beginning of the twentieth century, the transmission voltages grew rapidly to reduce transmission losses. To improve operating efficiency, power systems started to be interconnected. The reserve power or spinning reserve could be shared and capital expenditure could be reduced. One utility could supply power to another utility whose load was high at times when its own load was low. One of the prime technical problems in the past was the parallel operation of electrical machines.
How CIGRE started
CIGRE was founded in 1921. The Netherlands contributed to the activities of CIGRE right from the beginning. The Dutch delegation to the first meeting, in November that year, was headed by J.G. Bellaar Spruyt, who was elected Vice-President at that meeting. 1927 the organisation was structured by means of study committees (SC) and Dutch representatives played an active role in many of them. J.G. Bellaar Spruyt became the first chairman of SC 2 on High-Voltage Cables and was succeeded, after his death in 1929, by G.J. Bakker. J.C. van Staveren, founder of KEMA, acted as secretary of SC 2 for many years. Later on, van Staveren served as chairman and was succeeded as study committee chairman by R.F. Goossens in the early sixties.
The highest transmission voltage level in the Netherlands increased over the years from the 50-kV level towards a grid with connections at 110 kV, 150 kV, 220 kV and 380 kV. The Dutch National Mirror Committee’s of CIGRE took actively part in the technical journey of expanding power systems. Especially after the Second World War the economies were growing rapidly and the utilities had to meet a constantly increasing load. An important aspect of those times was the technological and engineering issues of power system operation.
The activities within CIGRE were over the years not only driven by the development of the Dutch grid but also by experts from the power industry in the Netherlands: Smit Transformers (which is still a leading transformer manufacturer today), the Dutch Cable Company NKF, Coq/HOLEC Switchgear (the first company to introduce Gas Insulated Switchgear), as well as several enterprises manufacturing Electrical Machines.
CIGRE’s Study Committee structure was adjusted a few times, reflecting the technical evolution of that period. In 1946, an Executive Committee was set up, National Committees were organised, and a technical periodical was issued. CIGRE working groups and task forces collect field data and perform system studies, and their reports are used as input for the revision of existing IEC standards. Today IEC and
CIGRE have formal technical liaisons, and many Dutch experts are members of the relevant working groups of both IEC and CIGRE.
The Early Meetings
The second meeting of CIGRE in November 1923 was attended by a delegation representing the Dutch utilities. Bellaar Spruyt, Smit Kleine, Bakker, van Staveren and a few others raised discussions about standards for overhead lines and underground cables for very high voltages and about communicating the danger of electricity to the public. At the meeting in June 1925 one of the topics was the concern about large turbo generators that were designed with a small transient reactance to improve the voltage stability of the grid. Bakker and van Staveren contributed by means of presenting a special AC-machine to study these phenomena. Measurements carried out on this analogue machine model confirmed the outcome of the mathematical exercises. Professor Hallo presented a report on the applicability of the method for determining dielectric losses of high-voltage cables to other electrical equipment.
Cables were already a major topic of interest in those days: cable circuits for 60.000 and 130.000 Volt were discussed and not only the construction of the cables but also how they had to be tested. Four or five times the nominal voltage or should one follow the French proposal: until 40.000 Volt tests with four times the rated voltage and above 40.000 Volt two times the rated voltage plus 40.000 Volt. Other scholars were in favour of relating the test voltage to the thickness of the insulating material.
At the fifth CIGRE meeting in June 1929 in Paris the Netherlands contributed on high-voltage cables (Bellaar Spruyt), test methods for electrical machines (Bakker and van Staveren), the shape of the generator voltage curve (Lohr and van Staveren), how to test transformer oil (Ornstein) and a report about losses in oil due to AC electromagnetic fields. At the sixth CIGRE conference in 1931 there were several Dutch contributions. One of them was a report regarding grounding and safety measures for low-voltage equipment by Ehrenburg and van Staveren. The seventh CIGRE conference was held in June 1933. Despite of the severe world wide economic crises 751 persons attended the conference. They represented 31 countries from 5 continents. From the 129 reports that were discussed the Dutch delegation contributed with two reports. A report about galloping lines and a report about the dielectric withstand capability of insulating paper.
The Conferences after the Second World War
The twelfth conference took place from June 24th till July 3rd 1948 in Paris. The topics were divided over four sections:
· Generation, transformation and interruption of electric current;
· Construction, insulation and maintenance of overhead-lines and underground cables;
· Operation, coupling and protection of electricity grids;
· Transmission of electrical energy at ultra high-voltages.
The Dutch delegation to the thirteenth CIGRE meeting in 1950 was under the supervision of G.J.T. Bakker and H.C.J.H. Gelissen. The delegation consisted of 34 participants and three reports were issued. H.A. Hidde Nijland wrote a contribution about fundamental aspects of metal enclosed switchgear. C.F. Proos contributed with a report about voltage curves and oscillograms of pressurized oil filled cables. D.T.J. ter Horst presented a report about transient recovery voltages in the Dutch 50 kV distribution grid and the 110-kV transmission network. Bakker acted as special reporter for cables.
At the 1952 conference there was a lively discussion about the Dutch contribution by Provoost about lightning impulse testing of transformers.
The general opinion in those days was that lighting impulse testing had become a mature testing technique and that was no objection to full scale testing anymore. The discussion focussed on chopped wave testing, which had still teething troubles and was considered to be in the developing stage. A second point of discussion was the question whether a lightning impulse test was sufficient to verify if partial discharges occur in transformer insulation and, if so, conclusions could be drawn about the quality of the transformer insulation as such.
For high-voltage circuit breakers three items were hot in those days.
· The rate of rise and the peak of the transient recovery voltage;
· The post-arc conductivity of the plasma channel after current interruption;
· Overvoltage caused by interrupting small inductive currents and by switching off unloaded overhead lines.
The actual waveform of the voltage oscillation is determined by the configuration of the power system. The transient recovery voltage or TRV is present immediately after the interruption of the current. When the TRV oscillation has damped out, the power frequency–recovery voltage is active. The duration of the TRV is in the order of milliseconds, but its rate of rise and its amplitude are of vital importance for a successful operation of the interrupting device.
In the early years of switchgear and fuse design, the TRV was an unknown phenomenon, the recovery voltage was regarded to consist of the power frequency–recovery voltage only. The duty on circuit breakers was commonly expressed in terms of the circuit voltage prior to short-circuit and the magnitude of the current in the arc. It was, however, experienced that, in practice, other circuit characteristics would affect the duty to an important extend. Improved measurement equipment, such as the cathode-ray oscillograph and later the cathode-ray oscilloscope, made measurements with a higher time resolution possible and revealed the existence of a high-frequency oscillation immediately after current interruption: the TRV was discovered. This resulted in system studies of transmission and distribution networks. Many investigations were carried out in different countries to determine the TRV across circuit breakers while clearing short circuits in networks to provide a base for standardization of the TRV in national rules for type tests on circuit breakers. System studies on transient network analyzers brought insight into the frequencies of oscillations and were verified by real tests in the network. Better understanding of the transient phenomena in the network has led to improved testing practice in the high-power laboratories, more accurate measurement of the current-zero phenomena, and consequently resulted in more reliable switchgear with a higher interrupting capability. During that period of time, the end of the 1950s, effort was made to represent the TRV oscillations by standardized waveforms to be able to create TRVs by lumped elements within the walls of the high-power laboratory.
In the early nineteen sixties, several network studies were undertaken in Japan and in Europe and attempts were made to better define the analogue modeling of the transient phenomena. The tests for TRVs were
specified differently in the various national rules, and Subcommittee 17 on High-Voltage Switchgear of the International Electro technical Commission (IEC) asked the Study Committee on Circuit Breakers (named Study Committee 3 in those days) to promote new extensive investigations on an international base. The engineers of KEMA’s high-power laboratory, the largest test facility in the world, played an important role in the standardization of transient recovery voltage wave forms and in the development of new test circuits and test techniques. D.Th.J. ter Horst and G.A.W. Rutgers made in those days a major contribution to the understanding of the post-arc current and reported their findings at CIGRE conferences.
The Cable Connection
The reasons why the Netherlands believed in cables from the early beginning were probably: the densely populated country, accessibility of wet soil, short distances and certainly last but not least because of the dominancy and the perseverance of the pioneer’s van Staveren, Proos and Bellaar Spruyt at that time, who were really “cable minded”.
After the 2nd World War the Dutch remained committed with CIGRE cable activities, continuing the tradition of offering a disproportionally large contribution to CIGRE in relation to the size of the country and its electricity grid. People like van Staveren (KEMA), Goossens (KEMA), Goedbloed (NKF), Kreuger (NKF) and Boone (KEMA) together with many colleagues contributed substantially to the work of the Study Committee, dealing with a great variety of subjects that were taken into consideration over the years and more than 80 years after the foundation of the cable commission the Dutch are still very active.
No one seemed to have problems with the relatively large input of such a, geographically, small country. One of the reasons probably was that in the Netherlands, from the beginning of electrification, underground transport of electricity was the preferred option. Overhead lines came later, when the higher voltages such as 110 and 150 kV were introduced, although the first 22 km long 150 kV connection between Rotterdam and The Hague was an underground oil filled cable circuit, installed in 1937/1938. Preceding the final selection of the manufacturer, several manufacturers were invited to offer their 150 kV cables to be tested in 1934 in a kind of long-term pre-qualification test at KEMA’s premises. CIGRE SC 2 was certainly the preferred body to discuss the results of this long-term testing of 150 kV cables, which was very advanced at that time.
The Dutch played a dominant role in the organization of the SC since 1927 as they delivered both chairman (Bakker, CEO of the utility of The Hague) and secretary (Van Staveren) for an extremely long period.
In 1927 Bellaar Spruyt, Chairman of the association of managing directors of utilities in the Netherlands, reported on the results of international standardization of HV cables at the 4th CIGRE conference. The discussion about this report resulted in the formation of an international cable commission with 37 members. Bellaar Spruyt became the first chairman of this cable commission. It was not surprising that three papers of nine in total on cables at the 1927 CIGRE were written by Dutch engineers.
In 1923 the number of papers on insulated cables was seven of which two were from the Netherlands. The Dutch delegation put at the agenda of the 2nd CIGRE the cable testing practice developed by van Staveren, founder of KEMA, and Proos, chief engineer of the major Dutch Cable Factory NKF. This combination of pushing power and technical expertise appeared to be very effective in promoting innovation. The testing practice of both pioneers Van Staveren and Proos was based on tan delta measurements to assess the degree of ageing of mass impregnated 10 kV cables, caused by partial discharges. This testing proposal implied a long-term testing procedure including heat cycles. However, the testing methods to improve reliability of HV cables developed in the Netherlands were controversial and it would take many years of ‘heated’ CIGRE discussions before the Dutch approach of long-term testing and related standards were internationally accepted. Different technical views, conflicting interests, and feelings of superiority of the key persons involved, gave these discussions an enormous intensity and unthinkable excitement. Opposition from French, German and Italian experts, who were in favour of short-term testing, was ongoing until in 1935 an agreement was reached. However, in 1938 at a meeting in Italy, the agreement was rejected by the Italian delegation, stating that the HV cable standards had to include oil-filled cables, invented by Emanueli in 1920, and internal gas pressure cables as well. Because of the 2nd World War, work was seriously delayed and international standards on cables were established after 1945.
The way of working of the SC changed from a place to discuss problems in the first years gradually to a body that manages work as efficiently as possible, to solve problems. Subjects for working groups are at present well prepared and when the decision is taken to start work, it has to be completed within a period of three years. An important change is certainly to listen more to the user of cables and to produce practical technical brochures to use.
When the Study Committee 21 “HV cables” celebrated its 75th anniversary on the 30th August 2002 in Paris, the complete Study Committee members and their guests, among them the acting President of CIGRE, the Secretary General of CIGRE, and all the still living past Chairman and past Secretaries of the SC, were invited on a banquet offered by the Dutch community to celebrate the 75 successful years of the Study Committee “Cables”. The Dutch representative in the Study Committee, at that time, said in his dinner speech: “when we add the years of Dutch chairmanship and Dutch secretary together, we ruled the SC for almost the whole period of 75 years, a lengthy period to be very thankful for and to take the opportunity now to do after all these years something in return.”
Study Committee Chairmen, Special Reporters and Working Group Convenors
CIGRE’s Study Committee structure was adjusted a few times, reflecting the technical evolution of that period. In 1946, an Executive Committee was set up, National Committees were organized, and a technical periodical was issued. CIGRE working groups and task forces collect field data and perform system studies, and their reports are used as input for the revision of existing IEC standards. Several Dutchmen served in recent years as SC-chairman, Th. Ykema and J.A. Wiersma for the SC on substations and J.J. Smit for the SC on materials for electro technology or served as special reporter like G.C. Damstra and A.L.J. Janssen for the SC on switching equipment. Many others contributed to working groups as convener or as member.