What is the impulse ratio?

The ratio of the flashover, sparkover or breakdown voltage of an impulse to the crest value of the power-frequency flashover, sparkover or breakdown voltage.

What is meant by impulse ratio of lightning arrester?

Impulse ratio of any lightning arrester is the ratio of breakdown voltage of the wave of special duration to breakdown voltage of a 50Hz wave.

What should be the impulse ratio of insulators and lightning arrester?

The impulse ratio of an sphere gap is unity due to uniform field, whereas for needle gap it may be 1.5 to 2.3 depending upon the frequency and gap. The impulse ratio of a gap of given dimension is greater with solid than with air dielectric.

What is impulse puncture voltage?

The impulse puncture voltage is the peak value of the impulse voltage which causes puncture of the material when puncture occurs on the wave tail and is the value of the voltage at the instant of puncture when puncture occurs on the wave front.

What is standard impulse?

Standard lightning Impulse is a full impulse having a front time 1.2 μsec and time to half value of 50 μsec. It is described as 1.2/50 impulse as shown in figure below. Standard switching impulse wave is characterized by prolonged wave-front and wave tail.

What is the purpose of impulse testing?

Impulse testing systems are designed to generate impulse voltages that simulate lightning strikes and switching surges. The complete test system consists of a charging rectifier, impulse stages according to the “Marx Circuit”, an impulse voltage divider and impulse voltage measurement system.

What are the different types of lightning arresters?

Difference between Lightning Arrester and Surge Arrester

Lightning Arrester	Surge Arrester
The types of lightning arresters are rod, sphere, horn, multi gap, electrolyte, and metal oxide.	The types of surge arrestors are distribution, low-voltage, station, DC, neutral protection, fiber tube, signal, network, etc.

How is LA rating calculated?

Voltage rating of LA = Line to line voltage × 1.1 × coefficient of earthing.

Which of the following is used for providing protection against incoming surges in lightning arrester?

The Surge Protection Device (SPD) is a component of the electrical installation protection system. This device is connected in parallel on the power supply circuit of the loads that it has to protect (see Fig. J17). It can also be used at all levels of the power supply network.

Which type of lightning arrester is used in substation?

Valve-type Lightning Arrester. A valve type of lightning arrester is used to protect the substations, line termination, and electrical equipment. This device discharges overvoltage (due to lightning) into the earth or earth grid.

What is impulse current?

Impulse Current Generation: Rectangular impulse testing is done to assess their surge energy absorption ability. Impulse current can have varying wave shapes and magnitudes depending upon their application and occurrence. Often, impulse currents appear as periodic or damped oscillatory currents.

How the impulse voltage is characterized?

IMPULSE VOLTAGE: 3.1. A full im-pulse voltage is characterized by its peak value and its two time intervals, the wave front and wave tailtime intervals defined below: The wave front time of an impulse wave is the time taken by the wave to reach to its maxi-mum value starting from zero value.

What is impulse ratio?

The concept impulse ratio is arises from Impulse voltage withstand test. It is an elecctrical insulation test. In this test, standard impulse voltage surge is applied to the insulator. Such surges are caused due to the lightning in practice.

How does a protective impulse gap work?

The protective impulse gap is designed to have a low voltage impulse ratio, even less than one and to extinguish the arc. Their working principle is very simple as shown in the figure below. It consists of two sphere electrode S 1 and S 2 which are connected respectively to the line and the arrester.

What is impulse ratio of protective device?

Impulse ratio of protective device is defined as the ratio of Breakdown voltage on Specified impulse wave to the breakdown voltage at power frequency. The concept impulse ratio is arises from Impulse voltage withstand test. It is an elecctrical insulation test. In this test, standard impulse voltage surge is applied to the insulator.

What is a gap in a rod arrester?

In such type of arrester, there is an air gap between the ends of two rods. The one end of the arrester is connected to the line and the second end of the rod is connected to the ground. The gap setting of the arrester should be such that it should break before the damage.