DLS (Direct Lightning Strike)
If a flash hits an overhead line, the current injected into the conductor is divided at the strike point, giving rise to two voltage waves that propagate in opposite directions. As a consequence, multiple flashovers occur between the conductors and also to earth in different points of the line. Customers around the fault location experience both a voltage sag during the short-circuit and a momentary interruption when the breaker opens to clear the fault. In the case of lines with covered conductors, the coating prevents the foot point of the power frequency arcing current from moving along the line, and therefore a flashover between phases for such lines may cause a mechanical breakdown of the conductors.
- Direct strike create a lightning impulse splitting and propagating along the line. It makes insulators flashover on its way
Strike location:
Poles / towers
Phase conductors
Overhead shielding wire
Parameters:
Average voltage 6 MV
Average current 30 kA
IOV (Induced Overvoltage)
Although the overvoltages associated with direct strikes to the line are much more severe, those induced by nearby lightning have a higher frequency of occurrence and are usually responsible for a greater number of line flashovers and supply interruptions on systems with rated voltage 20 kV or less. The induced voltage magnitudes and waveforms depend on many lightning parameters and are substantially affected by the network configuration. The evaluation of such transients entails the calculation of lightning fields, which are defined by the spatial and temporal distribution of the stroke current along the channel, as well as by the earth electrical parameters. The effects of a lossy earth and the case of multiconductor lines are also dealt with, and the influences of various parameters on the induced voltages are investigated.
- Indirect strike generate induced overvoltages on the line by electromagnetic effects. It can also lead to insulator flashovers
Strike location:
Trees
Buildings
Telecom towers
Parameters:
Voltage up to 300 kV
Sequence
- Direct strike create a lightning impulse splitting and propagating along the line. It makes insulators flashover on its way.
- Indirect strike generate induced overvoltages on the line by electromagnetic effects. It can also lead to insulator flashovers.
- After insulators flashovers, the current powered by a transformer at the nearest substation deviates from normal circuit: fault current establishes through the insulators affected by lightning overvoltage.
LQ Technology
LQ has its one unique technology and hereby are the steps of the process:
Stage 1: Lightning surge encounters the LQ.
Stage 2: The discharge channel expands (3), creating high pressure in the chambers. The sparks (4) between the electrodes (2) move to the surface of the insulation body due to the high pressure…
Stage 3: …and further blow outside around the LQ. Total resistance of the product is increased, enabling quenching of the fault current in less than 10ms.
1. Silicon rubber shape
2. Intermediate electrodes
3. Arc quenching chamber
4. Arc
5. Plasma jet
1. Silicon rubber shape 2. Intermediate electrodes 3. Arc quenching chamber 4. Arc 5. Plasma jet