Regardless of the numerous advantages of ZnO-based varistors, the impact of overvoltage often causes varying failures of these devices [ 20 ]. The repeated lightning strokes lead to the degradation of the structure of metal oxide surge arresters and, in consequence, deteriorate their electrical parameters [ 21 ]. For this reason, it is necessary to assess the technical condition of these devices. The aging process of varistors causes an essential increase in the leakage current (especially its effective component), which is widely used in diagnostic processes. In this article, we described the most important methods of the leakage current investigations and technical issues affecting the quality of these measurements.
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The electrical properties of ZnO-based varistors originate from the microstructure of these multicomponent ceramics. A typical chemical composition of these materials consists of ZnO (>95%), Bi(1%), Sb(1%) and trace amounts of other additives, which have a large impact on the electrical properties of varistors [ 5 ]. Metal oxide surge arresters have a typical ceramic microstructure and consist of semiconducting ZnO grains separated by pores and grain boundary layers, which are formed predominantly by Bi 6 ]. The dimensions of ZnO grains can be controlled by the addition of Sb, which crystallize in a spinel-like structure [ 7 ]. Furthermore, in order to improve the sintering process, NiO is usually used [ 8 ]. Other dopants modify the electrical properties of varistors, e.g., the upturn characteristic may be reduced by Co 9 ] and MnO [ 10 ], whilst Cr 12 ] promotes the nonlinearity of I(U) dependence. Moreover, Crwas found to lower the leakage current value [ 13 ]. Experiments were also performed with the use of other additives, e.g., alkali oxides [ 14 ] or rare earth oxides [ 15 ]. The parameters of the varistors depends not only to a chemical composition but also on the synthesis process. The value of Ustrongly depends on the size of the ZnO grains, which can be changed via the modification of the sintering time or temperature [ 16 ]. The high heating rate also increases the breakdown voltage; however, it may have a negative influence on the leakage current and the nonlinearity coefficient [ 17 ]. Moreover, the α coefficient is sensitive to the high sintering temperature, which is probably a result of the volatilization of Bi 18 ]. The dielectric losses are another parameter altered by the sintering temperature changes [ 19 ].
There are a few parameters used commonly to describe the electrical properties of surge arresters. One of them is residual voltage (U), which can be defined as a crest value of the voltage measured between the terminals of an arrester due to the discharge current having a current waveshape of 8 µs/20 µs. Another useful parameter is the leakage current (I), which stands for a current passing through the arrester during the tests at the maximum continuous operating AC voltage (U) [ 3 ].
Laboratory tests show that in ZnO ceramics, in the case of high-frequency waveforms of the order of 1 MHz, typical for lightning overvoltages, there is a maximum dielectric loss factor. An increase in the temperature of the arrester strongly favors an increase in its conductive properties. An increase in the leakage and polarization currents is then observed. In addition, aging with current surges causes a shift to the right of the voltage–current characteristics, which is physically associated with a change in the grain size distribution in the varistor volume—especially as a result of negative polarity surges. This phenomenon is related to the influence of temperature on the conduction mechanisms, especially in smaller varistors (e.g., low voltage), where relatively small exposures, due to weaker absorption of current surges, can cause strong heating of the varistor and change its U(I) characteristic, which shifts to the right towards larger currents [ 2 4 ].
For the voltage–current characteristics of the varistor in the initial range, it is observed at voltages forcing the flow of small currents (e.g., up to 1 mA ( Figure 1 , point (I1, U1)), with the resistance value of the varistor in the order of gigaohms. On the other hand, for a small change in the voltage, U, in the area of the so-called breakdown ( Figure 1 , point (I2, U2)), the current, I, reaches values of the order of kiloamperes, which is usually described by the power relationship (1):where k is a constant depending on the geometry of the varistor and its synthesis process, and α is a nonlinearity coefficient defined as α = [d (lnI)/d (ln) V] and usually lies in the range 30–100 [ 1 ].
The basic elements of the arrester are varistors made on the basis of zinc oxide ZnO (semiconductor) with many appropriate admixtures (mainly bismuth), which, as a consequence of the multi-phase structure, are characterized by non-linear voltage–current characteristics.
High voltage surge arresters have an important role in power systems, especially in protecting the insulation of power lines and transformers against lightning and switching overvoltages. However, in order to ensure an appropriate protection, it is necessary to cascade them with MV and LV ones, which is commonly known as a protection in depth. Their appropriate selection makes it possible to obtain proper insulation coordination between the electrical strength of the protected insulation and the level of protection clearly defined by the protective characteristics of surge arresters. A periodical inspection of the technical condition of the arrester allows the maintenance of the insulation coordination margin to be controlled and thus ensures the correct operation of the transformer in the conditions of voltage exposure. Information on the condition of surge arresters—similarly to other elements of the energy system—should be obtained already at the level of acceptance measurements so as to determine the operationally acceptable reference levels of the arrester’s quality indicators and the planned method of the earlier liquidation of elements characterized by poor technical condition. This approach allows for higher operational reliability of the energy system, in which emergency shutdowns of the network are undesirable phenomena due to the problems of maintaining the continuity of electricity supply to consumers.
At the level of LV and MV grids, the commercial power industry usually operates the surge arresters until they fail, and any checks usually force the voltage to be switched off, the surge arrester disconnected from the grid system, measurements carried out using external voltage sources, and a decision to replace or reconnect the apparatus to the grid. From the point of view of lightning and surge protection, it is periodically checked according to the internal operating instructions: in the scope of visual inspection—condition of insulators (cracks, scratches, traces of surface discharges), corrosion condition of fittings and connecting wires, damage or too high mechanical stress, number of surge arresters, value of leakage current, condition of earthing connections—condition of the conductor, continuity, corrosion, protective coatings. The result is an inspection card on which the condition of the device is entered: good, medium (within the scheduled date) and bad (immediate repair).
As part of a specialist or ad hoc review, specific lists of measurement activities can be proposed. This applies in particular to the area of power substations in the HV area, where power utilities have introduced their own inspection procedures consisting of testing surge arresters disconnected from the network or assessed online. Then, in order to assess surge arresters, the permissible levels of leakage current or reference voltage are given. For example, the manufacturer of the Tridelta arrester type SBK-II 96/10.2 expects a reference voltage level in the range of 101.6–106.3 kV when inducing a leakage current of a maximum value of 5 mA. In HV grid systems, the shutdown of the voltage is usually limited, and in this case, the activities are usually in the form of continuous measurements monitoring the technical condition of the surge arresters, especially in places providing overvoltage protection for distribution systems at the transformer/switching station (T/S_S).
Recommendations for the diagnostics of MV and HV spark-free surge arresters are provided in Appendix D to the standard [ 2 ], which contains guidelines for their use and selection. The standard applies to surge arresters that will be operated in three-phase systems with a nominal voltage above 1 kV. The supplement is a review of the methods widely used in the power engineering of the facility, unfortunately based on a literature review from the years up to and including 1993, and proposes the use of simple technical solutions consisting of the introduction of:
Damage indicators that do not disconnect the arrester from the network but only indicate the technical condition by indicating the amplitude and time of current flow or the temperature of the varistors;
Devices signaling the state of the partial or complete destruction of a varistor element (e.g., disconnectors);
Special devices measuring the number and/or amplitude of current and/or voltage surges;
Series spark gaps in the solutions requiring disconnection from the network or remaining in the network system;
Temperature analyzers;
Measurements of harmonic leakage current or active power losses.
Indicator devices are a component of a complete arrester or its additional element connected in series and are divided into fault indicators, disconnectors and operation counters. The damage of an indicator, in the case of exceeding the current amplitude or the duration of a certain critical current value, only indicates this fact without the automatic disconnection of the arrester from the network. The disconnector, in turn, is designed to isolate the arrester from the network system at the time of its failure. Typically, an explosive element (solutions for MV) is used for this purpose, triggered by the flow of a short-circuit current of a certain amplitude and duration. The disadvantage of the applied solution is the fact that after the arrester is disconnected, there is no overvoltage protection in the power network section until it is replaced.
Another way to determine the degree of degradation of the surge arrester is to use a trip counter triggered by a discharge current exceeding a certain amplitude. In the case of multiple discharges with times between discharges of less than 50 ms, due to the design of the counting system, not all discharges may be counted. In some designs, a sufficiently long follow-up current flow is required for the meter to work, which may cause difficulties in counting short discharge currents.
An interesting method of analyzing the state of the surge arrester is to use a thermal imaging camera. The intensive heating of the varistor structure causes a local increase in the temperature of the insulation of the housing, indicating problems with the varistor or water penetration into the housing and a local increase in surface currents in the varistor stack.
2 of the varistor element. The diagram given in the standard gives a typical U/Ur characteristic, indicating a leakage current of about 1 mA at a voltage of 0.6 Ur. Doubling the active component usually causes a slight increase of approx. 10% of the leakage current, which means that the main diagnostic effort goes towards the development of methods analyzing the active component of the leakage current, in which the third harmonic of this current has a significant share of the active current (from 10 to 40%).However, from the methods proposed by the standard [ 2 ], the methods based on the determination of the leakage current and its resistive component gained special importance in the online diagnostics of HV arresters and in the off-line diagnostics of MV and LV arresters. The standard specifies the level of the capacitive component in the range of 0.2 to 3 mA, depending on the capacitance of the arrester, which is typically 60 ÷ 150 pF per kV of the rated voltage, referred to as an area of 1 cmof the varistor element. The diagram given in the standard gives a typical U/Ucharacteristic, indicating a leakage current of about 1 mA at a voltage of 0.6 U. Doubling the active component usually causes a slight increase of approx. 10% of the leakage current, which means that the main diagnostic effort goes towards the development of methods analyzing the active component of the leakage current, in which the third harmonic of this current has a significant share of the active current (from 10 to 40%).
In most cases, in the power industry, there are methods that ensure the constant monitoring of the leakage current of limiters, unfortunately in the presence of frequent external disturbances. The standard for calculating the active component proposes various methods of leakage current analysis (e.g., a method of using a voltage signal as a reference, a method of compensating the capacitive component using a voltage signal, a method of compensation without using a voltage signal, a method of compensation using the analysis of currents in three phases and a harmonic analysis using the following methods: harmonic, third harmonic with harmonic compensation in the mains voltage and first-order harmonic analysis). Table 5 in [ 2 ] indicates that in professional practice, the methods of the analysis of the harmonics of the leakage current are generally used, the origins of which date back to the 1980s.
An undoubted advantage of the harmonic analysis method is the ability to measure the state of the arrester without disconnecting it from the network. Due to the significant error resulting from the content of the third harmonic in the supply voltage, even within the range of 100–350%, in practice, the method of third harmonic analysis with compensation with the signal related to the third harmonic of the limiter’s capacitive current has become the most popular. In practice, the method of measuring the leakage current based on the determination of the active component or the power of losses isolated on the arrester is most often used. Both the measurements taken with the surge arrester connected to the network (operational) and disconnected from the network (laboratory with DC or AC voltage) are used. In order to enable the measurement of the leakage current, a special insulated earthing clamp is installed between the arrester and the earthing, to which a measuring device is connected periodically (periodic diagnostics) or permanently (monitoring by recording the leakage current value on the memory card or in the supervisory system).
25,26,27,25,Currently, papers on the new numerically advanced methods of determining the active component are still being published. A review of the older and more innovative ideas is included in publications [ 22 23 ]. The work [ 22 ] lists innovative extensions created after establishing the content of Appendix D of the standard. These include works [ 24 28 ], which analyze various techniques for analyzing the current signal—both with only the total leakage current and additionally with a separate resistive component, allowing the amplitude and shift angles in the current signal for the components to be obtained—total and/or resistive [ 24 26 ], as well as leading to the determination of the shape and similarity of current signals recorded in a synchronous manner [ 27 28 ]. On the other hand, in the work [ 23 ], a number of improved classical methods have been compiled that allow its resistive component to be obtained from the current signal, specifying the limitations of their use, of which the presence of higher harmonics in the supply voltage was indicated in the first place.
30,31,32,33,34,35,36,37,38,New methods of determining the resistive components and their practical applications leading to the online diagnostics of limiters are still described in the literature [ 29 39 ]. For example, an interesting solution is the online method of measuring the resistive components proposed in [ 29 ], which uses a remote non-simultaneous method of measuring the resistive current (RNS). RNS remotely and non-simultaneously measures all types of resistive current parameters using remote, non-simultaneous phase difference measurement methods and specific harmonic analysis algorithms. The results of the simulation and the application of the proposed method showed sufficient accuracy, also in the conditions of frequency deviations and the presence of harmonic components in the supply voltage, which makes it possible to effectively use it in online diagnostics.
Great opportunities are offered by the machine learning method, which, by determining patterns of clearly defined damage, offers ways to effectively determine the following [ 27 40 ]:
Surface conductivity;
The deposition of metallic impurities.
For example, paper [ 40 ] describes the results of the analysis of surge arresters from operation with a rated voltage of 11 kV (continuous operating voltage 9 kV, rated discharge current 5 kA), which were artificially soiled on the surface using the SLM method described in the IEC 60507 standard [ 41 ]. This method uses a spray application of a mixture of NaCl and kaolin dissolved in distilled water. Using different compositions of the spray mixture, the different conductivities of the outer layer were obtained after the process of appropriate drying in a thermal chamber. The correctness of the applied layer in terms of its uniformity was confirmed by using machine learning to detect the dirt obtained at different concentrations of conductive material (5 levels) and relative humidity levels of 40% and 70%. During aging, an increase in the third harmonic of the leakage current and a decrease in HR, defined as the ratio of the fundamental harmonic to the third harmonic of the leakage current, was observed.
The measurements taken in the field were used to determine the lifetime of the limiters in the software and used in planning repairs. An example is the analysis [ 42 ] of the MOSA test results leading to the creation of a model combining ANFIS and the SVR model used at a later stage to determine the remaining life of use. A time series consisting of the leakage current and the value of the third harmonic component obtained from field measurements was used to teach and validate the implemented models. Forecasting models were qualitatively and quantitatively assessed using inspection graphics and an analysis of the adopted metrics for four different time horizons, respectively. In methods of this type, it is important to determine the correct criterion indicating the critical level of the exploited ZnO ceramics, for which physical and chemical tests are necessary, while also taking into account the statistical differences between the output parameters of new arresters and those of elements subjected to aging in complex exposure conditions.
An example of the test results obtained by the authors for two MV and LV oxide surge arresters is presented in Figure 2 and Figure 3 , respectively. The dispersion of the obtained values of the active component of the leakage current indicates the extreme variation in production quality and the related difficulties in arriving at unambiguous conclusions regarding eliminating the surge arresters from operation. In principle, this type of work should be carried out on specific control samples each time a batch of surge arresters is put into operation in power plants. This applies in particular to very poor-quality arresters, an example of which is shown in Figure 3 . The data collected in relation to the individual technical solutions and manufacturers could be used as reference data for the analysis of the operational results only in the case of observing the stability of the measurement results of leakage currents and reduced voltages. As can be seen from Figure 3 , for LV arresters, this kind of preliminary testing should be crucial even in the context of the decision to put the delivered batch of products into operation.
Figure 2 and Figure 3 indicate the need for power plants to perform commissioning tests with independent entities to confirm the repeatability of the basic parameters of the surge arresters used in the power system. Figure 2 and Figure 3 show the results of the active component of the leakage current for a 10-element sample taken from two different manufacturers of MV I LV arresters, respectively. The significant dispersion of the results of the active component of the leakage current shown in Figure 2 B for manufacturer B and in Figure 3 B for manufacturer F indicates possible problems in ensuring proper overvoltage protection during operation. The specified tests should be supplemented with the measurements of the reduced voltage in order to determine the correct quality of the arrester during operation at the rated discharge current.1, p2 and p3 are calculated using the Formulas (2)–(4):p 1 = I avg I max
(2)
p 2 = I h I max
(3)
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p 3 = I avg I max
(4)
1 ∈ (0.5; 0.76), p2 ∈ (0.01; 0.06) and p3 ∈ (0.01; 0.09) [In some countries, power utilities use methods for HV surge arresters that measure the following parameters of the leakage current: peak and average values and the content of harmonic components. On the basis of the determined values, the coefficients p, pand pare calculated using the Formulas (2)–(4):which should be included in the range p∈ (0.5; 0.76), p∈ (0.01; 0.06) and p∈ (0.01; 0.09) [ 43 ].
If the permissible values are exceeded, it is recommended to disconnect from the mains voltage and measure the leakage current at a DC voltage. In order to check the effectiveness of the above-mentioned method at the deformed mains voltage, when there are high distortions in the leakage current, additional tests can be performed to determine the suitability of the above-mentioned method in extreme operating conditions (e.g., rain and dirt).
Lightning Arrester is the device used to protect the insulation and conductors from damaging effects of lightning on electrical power systems and telecommunication. Typical Lightning Arrester has a high-voltage terminal and a ground terminal. When a lightning surge travels along the power line to the Arrester, electricity from the surge diverted through the Arrester to the earth.
If protection fails or is absent, lightning that strikes the electrical system introduces thousands of kilo Volts that may damage the transmission lines, and can also cause severe damage to transformers and other electrical or electronic devices. Lightning-produces extreme voltage fastens in incoming power lines would damage electrical home appliances that’s why it is essential to the principle of Lightning Arrester.
Presently the monitoring of total leakage electricity (capacitive and resistive currents) used by many utilities. The Leakage Electricity Monitors used to measure the Leakage Current of Surge Arrester, and in case of high leakage current Surge Arrester replaced. However, it is felt that this method is not the fool proof method as the total leakage current, which is purely capacitive, does not signify precisely the health of the Surge Arrester. There are the issues once the Surge Arrester has blasted even though total leakage current value was lower than the limit recommended by the manufacturers.
Resistive current is 15-30% of total current and since capacitive and resistive currents are at 90 degree face shift even reasonable change of resistive electricity results in very small increase in the total current. Hence observing total leakage electricity may not show degradation of ZnO disc. Degradation of long linear ZnO disc generally leads to harmonics in the leakage current when system voltage of fundamental frequency applied. Third consonant resistive electric measurement based on filtering of third harmonic element from the total leakage current. Leakage current of the order of about 500 micro amps is generally considered as safe.
The power loss can check by several methods given below:
The use of advanced diagnostic methods greatly decreases the chances of failure & avoids loses of man and money. It is desirable to check condition of Surge Arrester at regular time intervals, by measuring the resistive element of the continuous leakage current in service without decreasing energy of Arrester. Reliable measurements achieved by the instruments based on the principle of “Voltage Signal” as a reference. Regular monitoring of Lightning Arrester has prevented many failures in 66 kV to 765 kV substations. Advanced machineries promote testing even the Surge Arrester is in service, analysing with special current clip-on transformer leakage electricity in the Surge Arrester ground connection. The values of this current normally ranges from fractions of mille ampere to a few mille amperes entire characterized by a resistive current variation whose value is an indicator of deterioration of the Surge Arrester. Leakage of electricity increases due to different stresses like declining and Arrester failures.
Most building services would simply not function correctly if faults or defects were present but the correct operation of a lightning protection system only becomes obvious when it called upon to protect a structure. For this reason it is even more vital to make sure that fully trained and accredited engineers undertake regular testing and maintenance works on vulnerable structures and sites.
The current in a lightning strike is likely in the range of 2,000A – 200,000A and so an effective functional system is vital to make sure protection of assets. Majority of structures use BS6651 to report their design, testing and maintenance works related to lightning protection. This standard states a “competent person” should carry out inspections so a good rule of thumb is to look for contractors with third-party accreditation of their ability to design and report on lightning protections systems.
As large parts of the lightning protection system may be hidden or inaccessible after completion, it is particularly important, and indeed necessity of the code, that each element of a lightning protection system should inspect during the construction stages of an installation. Special attention must give to any part of the system that will hide conceal upon completion. These elements may hide for aesthetic reasons or the element would be necessary part of the structure. Inspections should carry out during the installation process but also upon completion and at regular intervals.
Visual inspection of an installation should take into account the following key points and observations recorded in the detailed inspection report:
This section deals with testing the earth electrodes on the system, although reference made to a visual or measured test of any joints or bonds. In practice, it is usual for inspections of components to undertake for testing to carry out.
Electrode testing needs experience and knowledge to make sure that any test carried out is meaningful and gives back resistance of electrode under test. Too frequent, Omega handed client information presenting resistance readings that are obviously continuity tests and not true earth-resistance tests. There are two suitable methods of testing lightning protection earths: ‘Fall of Potential/the 61.8% method’ and ‘Dead Earth’. Fall of Potential recommended method and involves the electrode under test; two reference electrodes, a set of leads and four-pole test meter. The electrode under test isolated and connected to the meter shown in figure two for the ‘Fall of Potential’ or figure three for the ‘61.8%’ method. In turn, the test meter connected to the two reference electrodes, which driven nearly 300mm into the ground and located typically 25 and 50 metres away from the electrode under test.
A test made and the direct resistance of the electrode under test recorded on the meter. This method, however, is only practical if the electrode to test located near to virgin ground where test electrodes can drive. In reality, in town and city centres, this is very often not the case. Presence of buried services and pipes may also influence on the test current and the last test value may corrupt as a result of these external influences. Reference electrodes should set away from such potential disturbances. Where practical conditions dictate that the ‘Fall of Potential’ method cannot be used, the ‘Dead/Known Earth’ method is really the only practical alternative. However, it is important to aware this method is open to error and misrepresentation if the test engineer is not competent to decide suitable dead earth or interpret the readings, which is why it is essential to use an Atlas accredited engineer to undertake tests of this nature.
The ‘dead earth’ could be any low-resistance earth not directly or fortuitously connected to the earth under test. A connection made from a suitable earth to the test meter, which is in turn connected to the electrode under test will show the lightning protection system acting as the known ‘dead/known’ earth.
A reading is then taken and the ohmic value achieved is effectively the series resistance of the electrode under test and the dead earth. The ‘Dead Earth’ method has some advantages when using the lightning protection system as the low-resistance ‘dead/known’ earth, as, due to the equipotential bonding need to other incoming services, it should give a low-resistance earth path.
Test clamps, or the clamp to the rod in the inspection pit, should open and the meter connected to the rod/rod side of the test clamp and the other side of the test meter connected to the system side of the test clamp. A reading can then be taken, which will show the series resistance of the electrode under test and the rest of the system together with other connected parallel electrical and other earth paths. As these other parallel paths usually have a relatively low combined resistance, the meter reading is effectively resistance of the electrode under test as, if correctly selected, the ‘dead’ earth that used is normally of such low value that it has little impact on final result.
In addition to providing an ohmic value for the electrode under test, this method also verifies the circuit to the dead earth source and by virtue of this, the electrical condition of the joints in the system. If the connections from the top of the test clamp to the air termination through to the other earths on the system and other parallel paths were loose or damaged, they would give a high resistance, which the meter reading would give back.
This situation should then be investigated so that any high-resistance joints can address. Where no access to an electrode is possible and, the pile foundations have utilized as the earth termination, it recommended that reference rods installed around the structure and tested upon completion. These do not necessarily form a part of the installation but may use as comparisons against the original pile foundation test results. In short, if the reference rod values have not increased year on year then it can assume neither resistance of the pile foundations.
The ‘Dead earth’ test method also applies to clamp-on CT type testers where disconnection is not needed, although this type of testing is not always practical. At least two types of test recommend one for each single electrode in isolation and a second for a combined value. The needs of BS6651 are an overall system resistance (excluding bonding to any services) of 10, and each electrode not exceeding 10 times the number of earth electrodes on the system. Any disconnection of the system should carry out with a test to make sure that it is not ‘live’ and no testing should carry out during storm conditions.
Failure to keep up to date, accurate records can result in hidden parts of a system not being adequately attended to and potentially unnecessary remedial works being proposed and executed, as a full assessment of the installation has not been made. At the time of the annual test and inspection, the following records needed either on site or in an accessible place.
BS6651 states that the following records should be kept:
In order to comply with the Construction Design and Management Regulations, these records should give at completion of the original installation for inclusion in the project Health and Safety file. The person responsible for the upkeep of the building should recover the lightning protection system records from this file and present them to the engineer undertaking the first post-installation inspection and test. Details of the inspections should record so that the needed information can updated and maintained. The programme of tests and inspections would analyse what, if any, maintenance needed. BS6651 states that attention should give to the following:
Statistics show the UK alone subjected to around two million strikes per year and, to make sure your lightning protection system is functional when called upon, bearing in mind you have no way of determining when that any maintenance work should be carried out with suitable expediency.
In the hands of experienced engineers, proper testing and maintenance of lightning protection systems can become a routine, but very necessary, part of a comprehensive safety programme. At the very least the consequences of not taking a thorough approach could incur unnecessary costs but, given the destructive potential of a lightning strike, those consequences could be much worse.
All lightning protection systems and static earthen systems must inspect and test by skilled person using calibrated test equipment. By law, this should carry out in line with the relevant standards (BS EN 62305) when the installation completed and on regular basis. Therefore lightning protection testing scheduled at interval of 11 months. Over twelve years, the protection system will test under all seasonal conditions – these can significantly affect performance due to changes in resistance and other characteristics.
Complete lightning protection testing would make sure that all structures, key electrical and electronic installations are safe from the effect of lightning strike. You will receive a detailed report that will include not only the findings of the test but also any recommendations for further protection.
Maintenance work and upgrades require if the testing and inspection reveals any deterioration in the level of protection or if any changes or additions to the structure contributed the existing systems inadequate.
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