Electric power industry consulting
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
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,
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
To protect the transformer from lightning surges, the metal-oxide arrester (MOA) is often placed directly at its bushings, at a distance of no more than 2-3 m. This creates an impression that the transformer will be fine. In fact, this is a false impression, and the effect on the windings depends not only on the
In the energy industry, many processes can not only be calculated on models, but also measured in an operating network. Measurements are important because they allow us to verify the models and, if necessary, adjust them. One of the areas where measurements in the network are practically impossible is impulse processes (lightning and switching). Therefore,
Let us discuss the length of the bonding cable and also such a thing as the steepness of current/voltage impulses that creates voltage drop. Industry documents suppose that the voltage in the joint can be determined as a sum of residual voltage of SVL (sheath voltage limiter) and the voltage drop across the bonding cable,
For high-voltage cable lines, the cross-bonding of screens is quite common. It is used not only for 110-500 kV lines, but also for 6-35 kV. The cross-bonding assumes that the six cable screens (1,2,3,4,5,6) must be removed from the three joints (A,B,C) and then connected to each other in a cross manner using a system
Medium voltage 6-35 kV grid usually do not have a solid neutral grounding, and a voltage of 50 Hz may occur on the neutral. Today let’s talk about why it may happen in the cable network even in normal operation, and how this can lead to Temporary Overvoltages (TOV) and damage to equipment. One of
When any element of the electrical network is energized, a transient process usually occurs. For example, when a voltage is applied to a power transformer, an inrush current of a magnetic nature occurs. The magnitude of the magnetization current of the transformer can reach several kA and sometimes causes serious concern. Today let’s compare inrush
Sometimes it is necessary to have several cables for each phase. For example, this happens when an overhead line (OHL) and a cable line are connected in series (see photos). Or it happens when we connect a transformer of a great power to the busbars (or consumers) using a cable line. Cable connections of overhead