Abstract: In the thunder and lightning protection process, by is struck by lightning the disturbance destruction which the electromagnetic pulse causes, at present the usual use electricity wells up the protector to realize to the micro electron equipment protection. On the international electricity wells up the metal zinc oxide valve piece which the protector uses mainly to adopt two connections methods: Is take America, England primarily adopts the multi- pieces metal zinc oxide parallel use the method, the use standard as UL1449 second edition, another is take the law, German primarily Germany adopts the monolithic metal zinc oxide technology the method, the use standard as IEC61643-1-2. The metal zinc oxide valve piece parallel use merit may obtain in a big way passes flows the capacity, after prevented the monolithic metal zinc oxide valve piece penetrates braves the smoke and the detonation, but Europe and the domestic some experts think the multi- pieces metal zinc oxide valve piece parallel use, because leaks flows, presses performance and so on sensitive voltage is inconsistent, creates the partition of energy non-uniformity, has the valve piece hot collapse. The author brought this these questions to perform the experiment in the American JOSLYN Corporation laboratory, has obtained some extremely valuable test data. The analysis thought that, The metal zinc oxide valve piece so long as carries on certain screening, pairs, and takes the suitable measure is may parallel use.
Key word: The thunder and lightning protection, the zinc oxide valve piece, the parallel use, tests the research

First, foreword
In the atmospheric thunder and lightning phenomenon can give humanity's survival and the social activity brings the harm, to its protection question always is people issue of concern. Along with the social economy and the science and technology development, the micro electron equipment widespread application, we not only Yao pay attention to the prevention to affect the building or other objects straight strike the thunder disaster, moreover to is struck by lightning the electromagnetic pulse (LEMP) the protection gives enough takes, at present in the domestic external implementation thunder and lightning protection process regarding the LEMP protection, usually is uses the electricity to well up the protector (SPD) (SURGE PROTECTIVE DEVICES) to limit the transient state 过电�?and the guidance releases the electric discharge to well up the electric current to realize [ 5 ] [ 6 ], now generally the main component which uses in SPD is: Metal zinc oxide (MOV) valve piece, electric discharge gap, gas or solid discharge tube, filter coil, transient diode (SIDACTOR) and so on, but uses in the low pressure line (220V ~ /380V ~) center SPD, the overwhelming majority uses the MOV valve piece. In low tension circuit in order to achieve 25 ~ 50ns high speed response time, on the international MOV valve piece diameter general control about 14 ~ 20mm, most greatly passes flows the capacity generally in 60 ~ 70KA, the current waveform is 8,/20 mu s. US in UL1449 second edition "Transient voltage Surge Protector Standard" TVSS (TRANSIENT VOLTAGE SURGE SUPPRESION) center suggested [ 7 ], use the multi- pieces MOV valve piece parallel use, achieved bigger passes flows the capacity. Because at present experiments in the domestic and foreign multi- pieces MOV valve piece parallel technology test and analyzes the research work not to be many, therefore uses for this technology in the thunder and lightning protection also has the different view. This article in view of the above question, attempts through in the American JOSLYN Corporation laboratory test experiment, as well as to the sample and the data analysis, produced to the multi- pieces MOV valve piece parallel technology use firmly answered.
Second, MOV valve piece main performance
The MOV valve piece principal constituent for the zinc oxide (ZnO), and infiltrates has the few other oxide compounds, the outer layer is composed [ 8 ] by two lead and a plastic coating, in the low pressure electrical power system, generally uses the circular the diameter is 14mm and the 20mm MOV valve piece. In the DC voltage is under 3KV, the electric capacity respectively is 5600PF and 22000PF, the nominal passes flows the capacity respectively is 4KA and 6.5KA, the current waveform is 8,/20 mu s. The MOV valve piece beginnings and ends voltage is lower than when presses the sensitive voltage, assumes the high impedance condition. When the voltage is higher than presses the sensitive voltage, as a result of the valve internal uneven natrium effect and the avalanche effect, rapidly assumes the low impedance. The voltage is lower than presses the sensitive voltage to return to the high impedance condition. Below the MOV valve piece quality mainly decides some parameters.
1st, presses the sensitive voltage
When the temperature is 20 �? generally thought has the 1mA electric current has flowed the time on the MOV valve piece, the corresponding Canada's is called on this valve piece voltage presses the sensitive voltage. Should according to the following formula computation:
Vn >= (VNII× �?2 /0.7) 1.2
In the formula: VN¨D¨DMOV valve piece pressure sensitive voltage value
VNH¨D¨D power source rated voltage value (有效�?
Presses around the sensitive voltage impact the rate of change to be supposed to be smaller than ±10%
2nd, leaks the electric current
The MOV valve piece continues the working voltage obscene valve piece in the nominal the electric current to be called leaks the electric current. Should be smaller than 30 mu A according to the national standard. Around the impact rate of change should be smaller than 200%.
3rd, remnant pressure and remnant pressure ratio
In the stipulation profile, the nominal discharging current impact zinc oxide valve piece, the valve piece beginnings and ends measured the voltage peak value, is called the remnant pressure.
The remnant pressure with presses the sensitive voltage the ratio, is called the remnant pressure ratio.
In the ordinary circumstances the remnant pressure ratio should <= 3.
Third, MOV valve piece parallel use
In under the guarantee high speed response premise, must enhance TVSS or SPD passes flows the capacity, generally adopts the multi- pieces parallel use. Europe and the domestic some experts think the multi- pieces MOV valve piece parallel use, because the valve piece performance is inconsistent, possibly has the thunder and lightning partition of energy non-uniformity, creates the MOV valve piece temperature increment, the performance drops, causes the hot collapse, or shifts to an earlier time the aging, the expiration, therefore did not advocate adopts the multi- pieces zinc oxide valve piece parallel use. But at present on international uses on the low pressure power source electrical power distribution system the monolithic MOV valve piece most greatly passes flows the capacity only to be able to achieve 60-70KA (8,/20 mu s) could not meet the actual project needs, therefore had the extremely vital significance regarding the MOV valve piece parallel use research.
Fourth, in American JOSLYN laboratory test data analysis
American JOSLYN Corporation is the thunder and lightning surge protection specialized company, started from 1950 specially to study the thunder and lightning and the instantaneous overvoltage protection. JOSLYN Corporation continuously has produced parallel MOV TVSS, the product since 1979 proliferates the world more than 130 countries the correspondences, the electric power, the transportation, the aviation, the finance, the computer network and so on. American presidents plane air force has used this company's product.
The author and American Dr. JOSLYN Corporation laboratory Hans Steinhaff has carried on the below test.
(1) measuring instrument
1st, Keytek 587 8,/20 mu s profile standard impact test meter.
2nd, Keytek S1/S3, S4/S5/S6 and S7 surge network element.
3rd, Peason 301x electron wide band electric current converter.
4th, 7A26 double trace amplifier.
5th, Tekronix7835 memory type oscilloscope.
(2) sample extracting
This experiment altogether extracts three groups of samples, A group stochastically extracts 50 piece of MOV valve piece from one batch of products; B group selects 1mA from one batch of valves pieces to press sensitive voltage most Gao Hezui low MOV valve piece each 25 pieces; C group is extracts from one batch of MOV valve piece product presses the sensitive voltage highest 25 pieces, extracts from another batch of products presses the sensitive voltage lowest 25 piece of samples. All MOV valve piece passes in the identical rank flows under the capacity to attack two times, table 1 had demonstrated is attacked after each group of MOV valve piece the electric current mean value and occupies joint current the percentage. In the table A1, A2 are selects every two piece of MOV valve piece from A group to match is a pair (altogether 25 pairs), after is parallel attacks after the identical electric current two time obtains the average value. B1, B2 are selects from B group presses sensitive voltage most Gao Hezui to be low MOV valve piece each piece to match is a pair (altogether 25 pairs), after is parallel attacks after the identical electric current two time obtains the average value. C1, C2 are selects from C group presses sensitive voltage most Gao Hezui low MOV valve piece each piece to match is a pair (altogether 25 pairs), after is parallel the average value which attacks after the identical electric current two time obtains.

Table 1 each group of MOV valve piece average current (A) and percentage
Surge current (A) A group of electric currents percentages % B group of electric currents percentages % C group of electric currents percentages %
A1 A2 A1 A2 B1 B2 B1 B2 C1 C2 C1 C2
12571665248114228416120168812
500250245514937013074263901008020
750380375505053022570305601807624
3000150014905050175012005941180012006040
10000475047505050525042005644540040005743
Table 2 had demonstrated around the MOV valve piece impact, 1mA presses the sensitive voltage change situation, and produced around the impact cathode 1mA to press the sensitive voltage the change.
Table around 2 impacts positive and negative 极压 sensitive voltage mean value (V)
Before after the sample impact attacks
Positive and negative positive and negative
A1 238.239240243 billion
A2 237.238239242 billion
B1 225.224224224 billion
B2 251.251251255 billion
C1 227.227226229 billion
C2 254.254248257 billion
(3)  data analysis
Is not difficult from table 1 to see, in A group of identical wholesales goods sample extracts MOV valve piece, even if has not passed through strict screening, pairs, no matter in 小电�?or the big electric current impact situation, on the parallel two piece of MOV valve piece absorbs energy basic balance, but in B group of identical batch of products, extracts MOV valve piece pressure sensitive voltage most Gao Hezui lowly to pair. In 小电�? (125 - 750A) under the impact, the energy which on two piece of parallel MOV valve piece absorbs is not balanced, biggest error in 84% and 16%. In big electric current (3,000 ~ 10000A) under impact, two piece of parallel MOV valve piece absorption energy basic balance, biggest error in 59% and 41%. C group extracts for the different raid in is highest and the minimal pressure sensitive voltage MOV valve piece pairs, in 小电�?(125 ~ 750A) under the impact, on two piece of parallel MOV valve piece the absorbed energy is not more balanced, the biggest error in 88% and 12%, also must be bigger than B group, but in the big electric current (3,000 ~ 10000A) under the impact, on two piece of parallel MOV valve piece the electric current also basically balances.

Fifth , the JOSLYN laboratory does other assistance tests
(1)th, recently JOSLYN Corporation wilfully extracts 6 from one batch of products respectively to use 3 piece of 20mmMOV valve piece parallel TVSS, the surge current is 1500A, the profile is 8,/20 mu s, passed through 10,000 times of impact tests (to record 2,500 tests), after 5 each TVSS passed through 10,000 times of impacts, under the 1mA pressure sensitive voltage rate of change <= ±10%, another after 8,500 impacts tests, under 1mA pressed the sensitive voltage rate of change > 10%.
(2)th, another test is parallel 4 piece of MOV valve piece, does not need sedulously to match, the surge current is 10000A, profile 8,/20 mu s, altogether attacks 220 times, then respectively before the test, center, latter 4 piece of parallel MOV valve piece 1mA presses the sensitive voltage rate of change is +7.3 ~ 7.5%, each piece of MOV valve piece 1mA presses the sensitive voltage rate of change is +5.3 ~ 6.7%.
(3)th, another manufacturer production TVSS, also uses the above similar method test, after 220 impacts, always 1mA presses the sensitive voltage rate of change is 12.4 ~ 20.9%, under the 10000A surge current, after a 40~60 impact, 1mA pressed the sensitive voltage to produce has been bigger than 10% change.

Sixth, conclusion
(1)th, because the MOV valve piece performance is inconsistent, specially under 1mA presses the sensitive voltage not to be inconsistent, can create under the impact the multi- pieces MOV valve piece is parallel when 小电�?(125 ~ 750A), each valve piece absorption thunder and lightning energy is inconsistent.
(2)th, in big electric current (3,000 ~ 10000A) under impact, even if MOV valve piece performance not too consistent, when multi- pieces parallel use each piece of MOV valve piece basically absorbs the thunder and lightning energy to be consistent.
(3)th, therefore, so long as slightly chooses to the MOV valve piece pairs, also using the fuse impedance help circulating current, the multi- pieces MOV valve piece is may parallel use, cannot not identically produce the heat generation because of the absorbed energy to collapse or to shift to an earlier time the aging.
Reference:
(1) R.H.Golde "Lightning" 1,997
(2) Su Bangli and so on "Thunder and lightning 避雷 Project" 1,998
(3) GB 50057-1994 "Building Anti-radar Design Standard" (in 2000 version)
(4) IEC61643-1 1,998 "Wells up Protector Connection to Low Electrical power distribution system Electricity" the first part of performance requirement and the testing method
(5) IEC61643-2/Ed1.0 2,000 "Connection Telecommunication Network And Signal Network Electricity Wells up Protector" the first part of performance requirement and the testing method
(6) IEEE "Low pressure Guards against Surge Installment Performance"
(7) UL 1,449 second edition "Transient voltage Surge Protector Standard" TVSS
(8) Peng Jinan, leaf Germany equality "zinc oxide linear resistance neutral electricity earth resistor" "Electric porcelaneous Arrester" 2001.6.