Author(s): Carlo Alberto Nucci & Fabio Tossani
Type:Technical Presentation
Date: 2021-09-07

Response of Overhead Lines to Direct Lightning Strikes: Assessment of the LEMP Effects852

Abstract
In the usual practice, the evaluation of the overvoltages due to direct lightning strikes to overhead power line conductors is focused on the representation of the effects of the lightning current inj... see moreection, whilst the effects of the coupling between the conductors and the lightning electromagnetic pulse (LEMP) is disregarded. Motivated by recent results obtained for the case of a medium voltage line configuration with a shield wire, this extends the analysis to assess the contribution of the LEMP on the lightning performance of an overhead distribution with and without periodically grounded wires and surge arresters. Moreover, the presentation deals with the LEMP effect on the occurrence probability of flashovers on different phases, which is an important information on the service continuity of networks with isolated or compensated neutral earthing. A validation of the results is obtained by comparing the overvoltages calculated by using EMTP, together with the LIOV library for the LEMP calculation, and those obtained by a three-dimensional finite difference time-domain approach.

Tag(s): lightning, pulse, LIOV, surge, arrester

Author(s): Rohit Kunte
Type:Technical Presentation
Date: 2021-09-06

Induced Voltage Study843

Abstract
MidAmerican Energy has conducted studies at some locations on our system to identify voltages that are induced due to lines on the same structures. For example, MidAmerican added a new 161 kV line fro... see morem substation D to substation E (not shown) through substation C. The line is mostly single circuit except between substations B and C where a second 161 kV line was added on the structures. There is also an existing 13.2 kV underbuilt distribution circuit on the structures between substations A to C.

The induced voltage study was performed to get an understanding on the level of voltages that may be expected when the 161 kV line from substation A to substation C is out of service, but the 161 kV line from substation D to substation C is in service and vice versa. The analysis provided very useful information on the level of induced voltages that may be expected on the 13 kV distribution feeder and helped MidAmerican to develop mitigation measures.

Tag(s): line, induced voltage, EMI

Author(s): Frédéric Colas
Type:Technical Presentation
Date: 2021-09-05

From FEMM to EMTP Cable Data – How to Use FEMM to Compute the Power Cable Parameters839

Abstract
In the context of the simulation of an electrical network, different models of lines / cables are available. Among these, we can cite the PI models, the frequency dependent models (FD-Line) or the mod... see moreels called Wideband. This last type of modeling is considered in the power system community as a sufficiently precise model to simulate the behavior of the cable under non-symmetrical faults and more particularly in the case of underground or submarine cables. However, the parameters of this type of model are generally still calculated from a standard geometry.

In this presentation, a methodology to obtain, from the software FEMM, the cable data parameters needed for EMTP will be presented. This methodology allows to easily obtain the correct parameters from specific cable geometry.

Tag(s): fem, cable, parameters

Author(s): Mr. Suyash Kulkarni - Mr. Suved - M. Pakade
Type:Technical Presentation
Date: 2021-09-03

Ground Fault Detection and Feeder Protection of 2x25kV Railway Traction System840

Abstract
In a new 2X25 kV System, Scott transformer is used as a traction transformer and to supply the power to the railway traction system. It is protected using the percentage differential relay.

... see more
However, region from the low voltage side of the Scott transformer to the first autotransformer is unprotected at the field and to protect the system during fault on this region is very important. Thus, development of protection scheme is required. Herein, we modeled 2X25kV traction system in EMTP, simulate faults and developed a specific relationship to provide the protection for this scheme. We have taken the current input from feeder current transformers and observed its current during the faults.


This performance of this scheme is verified using EMTP. Further, impedance to distance ratio is non-linear due to the autotransformer between catenary, rail and feeders in 2x25kV railway traction system. To observe this behavior as per field details and provide the accurate relay setting, we simulate the faults over the length of protected line in EMTP and field test are carried out. In the event of a fault on unprotected region and on the protected line, trip occurs and relay recorded fault details at the field.

Tag(s): Fault Detection, protection, railway, traction

Author(s): Aboutaleb Haddadi
Type:Technical Presentation
Date: 2021-09-02

Ground Fault Overvoltage with Inverter-Based Distributed Energy Resources841

Abstract
A Ground Fault Overvoltage (GFO) can occur in situations where an ungrounded transmission line and associated ungrounded transmission equipment is energized from distribution connected Distributed En... see moreergy Resource (DER) during a transmission single-phase-to-ground (SLG) fault. The condition could result in 1.73 pu overvoltage on phase to ground connected equipment which will be sustained until the DER ceases to energize the substation distribution transformer. Transmission equipment on the isolated circuit will be subjected to the above phase to ground overvoltage, also if there is frequency shift, the isolating transmission circuit breakers could potentially see up to 2.73 pu phase to ground overvoltage. Such an overvoltage can cause damage to customer or utility equipment and must be avoided. GFO concerns are already becoming a barrier to large-scale DER deployment either by posing low hosting capacity or by necessitating installation of costly mitigation equipment. Utilities need to study GFO risks and identify low-cost mitigation options to enable large-scale DER deployment. Given the fundamental differences in mechanisms and phenomena driving a GFO under DERs, classical GFO analysis methods do not apply to inverters, and advanced simulation methods and tools are required.


This presentation highlights EPRI’s work on GFO analysis, concerns, and evaluation of mitigation options using EMTP. The objective is to determine if or when high DER penetration presents a GFO problem and how to prioritize the mitigation and equipment evaluation. This includes evaluating the impact lightning arresters can have in reducing or clamping the overvoltage, the application and performance of high voltage substation overvoltage protection, and DER on-board voltage/frequency protection. The presentation further provides modeling recommendations for such a study using EMTP. As DER deployment increases, utilities will need to perform similar analysis to identify potential overvoltage risks and develop low-cost mitigation methods. This work provides a basis for such a study.

Tag(s): gfov, tov, ibr, DER, inverter, islanding, load rejection, inverter based resources