1.*Lighting Arrester*

2. Summary What is LightningArrester. Types of LightingArrester. a- Expulsion type b-Valve type arrester c- Gapless metal-oxide type Classification of Lighting Arrester a- Station class b- Intermediate class c- Distribution class d- Secondary class Identification Standard Ratings Service Condition a- Normal Service Condition b- Abnormal Service Condition 3. What is Lightning Arrester Lighting Arrester:- A device designed to protect electrical equipment from high transient voltage and to limit the duration and frequency the amplitude of follow-current. Surge arrester are usually connected the electrical conductors of a network and earth though they may sometime be connected across the windings of equipment or between electrical conductor. 4. Types of Lighting Arrester Originally, three types of surge arresters. They are: 1. Expulsion type; 2. Valve type arrester; 3. Gapless metal-oxide type; Ref-http://www.geindustrial.com/Newsletter/lightning_arresters_guide.pdf 5. Expulsion type This type of arrester is also called protector tube and is commonly used on system operating at voltages up to 33kV. It essentially consists of a rod gap AA in series with the protector tube. The upper electrode of protector tube is connected to rod gap and the lower electrode to the earth. Advantages:- 1- They are not very expensive. 2- They can be easily installed. http://www.circuitmaniac.com/2009/03/21/expulsion-type-arrester/ 6. Valve Type Arrester Valve type arresters incorporate non linear resistors and are extensively used on systems, operating at high voltages. It consists of two assemblies (i) series spark gaps and (ii) non-linear resistor discs in series. The non-linear elements are connected in series with the spark gaps and earth. The non-linear resistors have the property of offering a high resistance to current flow when normal system voltage is applied, but a low resistance to the flow of high surge currents. 7. Gapless metal-oxide type The gapless metal-oxide type arrester are the most widely used today. The metal oxide lightning arrester is the most advanced over- voltage protector. It is widely used as protective devices against switching and lightning over voltages in power electrical systems such as power transformers ,distributors, generators, compensation capacitors. 8. Classification of Lighting Arrester There are four classifications of surge arresters. i. Station class ii. Intermediate class iii. Distribution class(heavy, normal and light duty) iv. Secondary class The station class surge arrester is the best because of its cost and overall protective quality and durability. It has the best protection level and energy discharging capability with successively higher protection levels for the other classifications. 9. Nominal discharge current-Peak value of lightning current impulse which is used to classify an arrester. Surge arrester are classified by their nominal discharge current. Station class for 10,000A arresters; Intermediate(Series A) for 5,000A arrester Distribution(Series B) for 5,000A arrester Secondary for 1500A arrester IS 15086-44-SURGE ARRESTER(Part-1),clause 3.1 10. Identification Surge arrester shall be identified by the following minimum information which shall appear on the rating plate(nameplate): 1- Rated Voltage; 2- Rated Frequency 3- Nominal Discharge Current(Specifying for the 5 000A arrester whether series A or B, and for the 10 000 A arrester, whether light or heavy duty) 4- Long-duration discharge class(for 10 000 A heavy duty arrester) 5- Manufacturers name or trademark, type and identification. 6- Year of the manufacture. 11. Standard Ratings Standard values of rated voltages for arresters(kV r.m.s.)are specified in table 2 in equal voltage steps within specified voltage ranges. Standard rated frequencies are 50Hz and 60Hz IEC-60099-44_Surge arrester, clause 5.1&2 12. Service Condition 1- Normal service conditions:- Surge arresters which conform to this standard shall be suitable for normal operation under the following normal service condition; a- Ambient air temperature within the ranges of -40C to +40 C; b- Solar radiation; c- Altitude not exceeding 1000m; d- Frequency of the A.C. power supply not less than 48 Hz and not exceeding 62 Hz. e- Wind speed 34 m/s 13. 2- Abnormal service conditions:- Surge arrestersubjected to other than normal applicationor service conditionsmay required special considerationin design, manufacture or application.The use of this standard in case of abnormal service conditionsis subjectedto agreement between the manufacture and the purchaser.A list of possible abnormal service condition is given. Temperature in excessof +40C or below -40 C. Altitude higher than 1000 m. Nominal system frequency below 48Hz or above 62Hz. Unusual transportation or storage. Abnormal vibration or mechanical shocks.