Iec 60815 Pdf Free Download

[Giovanni Sealy]

Revision of IEC 62217-2012 and IEC TS 60815-1/-2/-3:2008 started from 2017 under IEC TC 36 MT19 and WG11. This edited contribution to INMR by LIANG Xidong of Tsinghua University in Beijing introduces the main revisions and related explanations so as to better understand the revisions of these two important documents in the field of outdoor insulators.

The purpose of IEC TS 60815 series is to provide a guide for the proper selection and dimensioning of overhead line and substation insulators. The first edition of IEC TR 60815 was published in 1986 [1]. Its revision started in 1997 and lasting for more than 10 years. The goal of the revision in 1997 was to make the technical document applicable to both a.c. and d.c. systems, as well as to insulators made from different materials, containing ceramic, glass and polymeric insulators. The second edition of IEC TS 60815-1/-2/-3:2008 are the current version under revision [2,3,4]. The revision of the second edition launched in 2017. The technical structure remains the same.

The difficulties of the revision come from several aspects. The first one is the proper evaluation of pollution environment. Natural pollution and wet situation differ from place to place. The second one is about power system operation experiences and maintenance regulations which differ from one utility to the other. The third one is about the tradition and habit of insulator selection and application, which also differ from one utility to the other. All these differences increased the difficulties of the revision work. Moreover, IEC TS 60815 series is not a design code for line and substation project. It is a guide in general. Sometimes it provides suggested result and sometimes it only provides a method for users to find their solution. It is not easy for readers with different background to correctly understand the technical document, and to understand the way to describe and organize the contents.

Pollution and wet conditions are different from one place to the other in a big area. Insulators with different profiles accumulate different site pollution severity (SPS) even they are located at the same place. Pollution withstand voltage for different insulators are different even if they are artificially polluted to the same pollution level. These three key issues make the proper insulator selection and dimensioning a very complex and very difficult work. Therefore, the evaluation of site pollution severity (SPS) is normally using classified results rather than exact ones.

Pollution measurement is quite a big topic. Before the starting of pollution measurement, there are three approaches proposed in IEC TS 60815-1:2008 [2]. Approach 1 is based on experiences. If previous experiences on insulator selection and dimensioning are satisfied, this experience can be followed and no pollution measurement is required. Approach 2 and 3 are based on pollution measurement. The artificial pollution test will be performed on selected and dimensioned candidate insulator if budget and time are allowed in approach 2. Nevertheless, there is no confirmation through artificial pollution test in approach 3.

In many cases, users will find that they have some experience but not sufficient to follow approach 1, and they took some measurement but not sufficient to follow approach 2 and 3. Then a combination of both approaches seems necessary and helpful.

Environment pollution type and severity are evaluated by different methods, mainly through the measurement of pollution accumulated onto the reference insulators, to obtain the pollution class. This is the work in IEC TS60815-1.

Then, the unified specific creepage distance of reference insulator (RUSCD) is suggested according to worldwide experience under a.c. condition, shown in Fig. 2. This figure is important for insulator dimensioning as well as for IEC TS 60815 series. It comes from tens of years worldwide experiences and it is familiar to worldwide utilities.

The shed profile of the candidate insulator is selected according to the pollution type. Then the USCD of the candidate insulator is dimensioned after several corrections of RUSCD, say shed profile correction, diameter correction, altitude correction and multiple string correction. Artificial pollution test is performed to confirm the result of insulator selection and dimensioning in approach 2. This is the work in IEC TS 60815-2/-3, shown as in Fig.1.

Table 5 in IEC TS 60815-1:2008 on the description of typical environments is helpful for the overall evaluation of pollution class after pollution measurement while its importance may also be ignored. In this revision, the table is slightly revised and renumbered.

1.4 SPS, SPS Value & SPS Class
Site pollution severity (SPS) was introduced in IEC TS 60815-1:2008. The concept of SPS actually contains two meanings, namely SPS value and SPS class. SPS value is the measured results from reference insulators, while SPS class is obtained after overall judgement sometimes. For type A pollution, SPS value includes both ESDD and NSDD. However, in the 2008 version, SPS value and SPS class were not distinguished, which is inconvenient in actual use. In this revision, a clear distinction was made between SPS value and SPS class.

After the measurement of SPS value from reference insulator, i.e., ESDD/NSDD for type A pollution, SES for type B pollution, SPS was classified into Class a, b, c, d, and Class e from very light, light, medium, heavy and very heavy in the 2008 version. Some users worried that USCD of Class e (say 53.7mm/kV in figure 2) could not prevent flashover in some extremely polluted conditions. Then a new name of pollution class, extremely heavy Class f, is added in this revision at the top-right corner of Fig. 4. Class f is only for some special situation of extremely heavy pollution when the USCD of Class e cannot meet the requirements. The corresponding USCD value is not assigned to Class f in this revision.

In Fig. 4, ESDD/NSDD were measured on non-energized reference insulators. The pollution accumulation of non-energized reference insulator is closer to that on energized one under a.c. voltage (of course they are different), when compared to the situation energized under d.c. voltage. Therefore, the title of figure 4 was marked with under a.c. voltage. It is only to remind readers that the pollution accumulation under d.c. voltage will be significantly different from the situation of non-energized insulators.

Reference insulators for type B pollution, both cap-and-pin and long rod insulators were added in this revision. The content of pollution measurement by directional dust deposit gauge (DDDG) was updated in this revision.

1.5 Pollution Measurement & Pollution Map
In IEC/TS 60815-2008, the SPS is determined by direct measurement on polluted reference insulators. It sounds perfect compared to the rough judgement from pollution environment. However, it must be noted that the less measurement points may result in false SPS description. On the other hand, many measurement points need a huge workload. Only when the measurement is carried out at the right place and right time, and the measurement is sufficient and the results are accurate, the measurement results can be used to determine the SPS class. Improper measurement of pollution will lead to improper pollution class judgement.

Several specification and suggestions about proper pollution measurement on reference insulators were specified and suggested in the 2008 version and this revision. But the setting of proper measurement location was not mentioned. The drawing of pollution map is very helpful for proper pollution classification after pollution measurement. Unfortunately, pollution distribution map is not available for current revision. CIGRE just launched a joint working group CIGRE JWG C4A3B2B4.75 to deal with the pollution map in 2023, which will conduct a systematic review of pollution measurement and pollution map drawing. Hope the result could be used in next revision of IEC TS 60815 series.

Fig. 5 shows the example of measurement result, Fig. 5a, and overall evaluated local pollution map, Fig. 5b. The dispersion of SPS measurement value is inevitable, not because of measurement errors, but resulted from the randomness caused by very local environments around reference insulators. In practice, insulators used within a certain region quipped with the same or similar creepage distance. It means that only one pollution class is recognized in one region. It is thus not practical to determine SPS class directly for each single measurement point. Instead, SPS class should be determined by considering measured SPS values, type of pollution, wetting characteristics, and operation experiences, taking the operation experiences as the priority factor to determine the proper pollution class for this area [5].

1.6 Correction from RUSCD to USCD of Selected Candidate Insulator
After the determination of pollution class, RUSCD can be determined based on the reference insulator according to the SPS class from IEC TS 60815-2/-3, as shown above in figure 1 and 2. According to the type of pollution, a suitable candidate insulator can be selected considering the profile. Then the correction from the RUSCD of the reference insulator to the USCD of the candidate insulator is needed considering four factors: profile, altitude, diameter, and the number of insulators in parallel, as shown in Equation 1.

It should be noted that the reason for the correction still comes from the pollution measurement. The measurement is based on the reference insulator. However, the candidate insulator is different from the reference insulator, so correction is required. In this revision, Ks and Kp are newly introduced, Ka is slightly modified and there are still many discussions for Kd.

When the profile is obviously different, the USCD may be different from RUSCD. The correction factors are still under study. Kp is 1.1 when there are many insulators in parallel, e.g., transmission line sections with more than 100 strings and is assumed to be polluted to the same degree and affected by the same pollution/wetting event. Kp is 1.0 when there are few insulators in parallel, e.g., station insulators and apparatuses.

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