Dynamic State Estimation Based Protection Case Study

DSE BASED ZONE PROTECTION:
The dynamic state estimation based protection (also known as setting-less protection) has been inspired from the differential protection function and can be considered as an extension and generalization as illustrated in Figure 1. In current differential protection the electric currents at all terminals of a protection zone are measured and their weighted sum must be equal to zero (generalized Kirchhoff’s current law). Thus the current differential protection function consists of measuring the sum of the currents and as long as it is zero or near zero no action is taken. In dynamic state estimation based protection, all existing measurements in the protection zone are utilized. These measurements include: currents and voltages at the terminals of the protection zone, currents and voltages inside the protection zone (as in capacitor bank protection), speed and torque (as in rotating machinery), or other internal measurements including thermal measurement. All above measurements should obey the physical laws for the protection zone (physical laws such as KCL, KVL, motion laws and thermodynamic laws). The physical laws of the protection zone are captured in the dynamic model of the protection zone.
This means that in absence of an
Following a failure of the ac voltage input there would be a misrepresentation of the phase voltages on the power system, as measured by the relay, which may result in maloperation. The VTS logic in the relay is designed to detect the voltage failure, and automatically adjust the configuration of protection elements whose stability would otherwise be compromised. A time-delayed alarm output is also available. There are three main aspects to consider regarding the failure of the VT supply. These are defined below: Loss of one or two phase voltages Loss of all three phase voltages under load conditions Absence of three phase voltages upon line