EMTP Simulation Test Cases

Assume that the example cable in Section 3.2.4 is buried as a singlephase cable, and find the impedance and admittance matrices for the single-phase example cable using EMTP. Use the Bergeron model and calculate the impedance and admittance matrices at 1 kHz. 

From the impedance and admittance matrices found in (1), find the phase constants for the earth-return mode and the coaxial mode 

Find the propagation velocity for coaxial mode and calculate the propagation time when the cable length is 12 km. 

Using the cable data created in (1), find the propagation time for a 12 km cable with EMTP and compare it with the propagation time theoretically found in (3). Assume that the sheath circuit is solidly grounded with zero grounding resistance at both ends. 

Propagation time of the 12 km cable found by EMTP simulation. 

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At this time, there are a number of numerical simulation tools that are widely used throughout the world to analyze a transient in a power system. Among them, the most well-known and widely used tool is EMTP. The accuracy and reliability of the original EMTP has been confirmed by a number of test cases since 1968. However, there is no perfect simulation tool in this world. Any simulation tool has its own application limits and restrictions. As previously discussed, the EMTP, based as it is on a circuit theory under the assumption of TEM mode propagation, cannot give an accurate solution of a transient associated with non-TEM mode propagation. Such application limits and restrictions are discussed in Chapter 8 for both circuit-theory-based approaches and NEA methods. 

Quite often, a problem appears unexpectedly for a user but not for the developers of a simulation tool it is hard for developers to predict such problems at the development stage. These problems are caused quite often by the misuse of the tool by the user. Therefore, reliability and severity tests of simulation tools are very important. For example, it took nearly 10 years to carry out reliability and severity tests on tens of thousands of cases with EMTP cable constants. It should be noted that the reliability of a tool (that is, the probability of a problem occurring) is proportional to the number of elements (that is, the number of subroutines and options) although each individual element has very high reliability. Input data often cause numerical instability when the data physically do not exist this problem is related to the assumption of formulas adopted in the simulation tool as explained in Section 8.1. To avoid such a problem, a KILL CODE is prepared in the EMTP. The kill code judges whether the input data are beyond the limits of assumption. It may be noteworthy that nearly half of the EMTP codes are kill codes. This may be considered by developers in another simulation tool. 

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