Electric power industry consulting
Let us continue with a series of green posts on transients and surge arresters. Today let us assume that, in three-phase network, a single-phase-to-ground fault occurs, in phase A. In this case, the 50 Hz voltage on the two undamaged phases B and C will increase compared to its normal value. Compared to normal operation,
For medium voltage (MV) line, usually, screens of single-core cables are grounded at both sides. Let us assume that we have two separate MV lines, differing in the mutual arrangement of three single-core cables:Line 1️⃣ – trefoil;Line 2️⃣ – in row. In the conditions of the example, according to the book, we get the following
The main characteristics of the three-phase AC network are its voltage class, frequency, and method of neutral grounding. Speaking of voltage, there are two different voltages (the designations may depend on the country):✅ Rated voltage (let it be Ur);✅ Maximum continuous operating voltage (let it be Umcov). Both voltages are the effective value of the
One of the ways to reduce lightning outages of overhead lines (OHL) is to place surge arresters (SA) on problematic sections of the line. However, there is always a risk of damage to the SA itself which creates a new problem. For example, damage can happen for one of the following reasons:✅ Lightning can transfer
Let us continue the series of green posts. There is such a thing as “temporary overvoltages” (TOV), and one example of such processes is ferroresonance. Ferroresonance, like ordinary resonance, occurs in circuits containing capacitances and inductances. However, unlike resonance, with ferroresonance, it is important that the inductance does not remain constant, but changes depending on
Electrical parameters of cables are an important topic. For each line, it is necessary to determine the longitudinal resistance (R) and inductance (L), as well as the transverse capacitance (C), and all these parameters (R,L,C) should be found not only in a positive sequence, but also in a zero sequence. For overhead lines, these parameters
It has always been obvious to me that in terms of thickness, there are two types of outer sheath of high voltage (HV) and extra-high voltage (EHV) cables:✅ Ordinary sheath – it has a thickness of about 5 mm.✅ Reinforced sheath – it has a thickness of about 6-7 mm.However, when I started trying to
We know that the screen’s cross-bonding is an effective way to deal with induced currents and losses in the screens of 6-500 kV cable lines (CL). The use of cross-bonding allows not only to save on losses (dozens of thousands of euros annually), but also to increase the permissible core current of the cable line,
It is not enough to have money to buy a good cable. It is also important to find the time and knowledge to make the necessary calculations and select the best way to lay a cable line, taking into account the screen bonding type. Today, let’s look at a simple calculation example of a double-circuit
For lines with single-core cables, there is a problem of selecting the optimal screens’ bonding type. It is especially relevant for 110-500 kV lines, where grounding of screens on both sides is almost prohibited, and 99% of lines have either grounding of screens on one side or cross-bonding of screens. In both cases, it is