Special Publication REGSys™ Parallel Regulation of Transformers The regulation of transformers with tap changers is a classical subject within the field of power supply and distribution. Today these tasks are accomplished electronically with high regulation quality. Digital regulators, such as the freely programmable REGSysTM voltage regulator system, are in use. * from etz Electrical engineering and

REGSys™ Parallel Regulation of Transformers The core of the REGSysTM voltage regulator system (Figure 1) is the REG-DTM voltage regulator which, in addition to its actual regulating function, also performs measuring, recording and statistical functions. The parameterization of the re- Figure1 The REGSysTM voltage regulation system consisting of voltage regulator REG‑DTM, monitoring unit PAN-D and SCADA communication card REG-PED in a 19“ mounting rack gulator can be carried out menu-driven either directly via the keyboard or via PC with the help of WinREG software. The communication interfaces...

BA BE BIN‑D E‑LAN EOR‑D MMU‑D PAN‑A PAN‑D Figure 2 An overview of the REGSysTM be disregarded, such circulating currents are also called circulating reactive currents. Even more complicating is the fact that the voltage regulation loses sensitivity, since a change in the individual opencircuit voltages u1 to ux only partially effects the total voltage of the busbar. If it is assumed that the impedances Zsc1 to Zscx are all equal and one of the transformers is upset by ∆ux in order to regulate the voltage, it follows that: variables must be found which can be used for the parallel regulation....

Master-slave and Master-follower procedures These procedures regulate on the same tap positions of the transformers. In the process, one regulator takes over control while the other regulators follow its position commands (master-slave regulation). In the master-follower procedure, the slave is equipped with additional intelligence. It can actively read the tap position of the master via E-LAN and can independently position itself to match the master’s tap position. A desired tap difference existing at the beginning of the parallel regulation between the master and the slaves remains intact in...

Integration into the voltage regulation As has already been illustrated, voltage regulation is not sufficient for the regulation of transformers connected in parallel. In order to avoid circulating reactive currents, the regulation of circulating reactive currents is superimposed over the voltage regulation (Figure 7). This results in the manipulated variables Yu and Yp at: YU = ( Uact – Uset ) / ∆Uperm YP = Icir Qx / Icir Qperm In addition, the following is valid for the resulting manipulated variable Y (see Figure 7): The control commands for the regulation are derived from equation (13) as...

Safety precautions In all of the procedures (with the exception of the cosϕ procedure), the regulators involved in the parallel connection all exchange the necessary data via the E-LAN. If the E-LAN connection is interrupted, reliable regulation must continue to be guaranteed. Since the ∆cosϕ procedure functions without any bus connection, it is applied as an emergency program. This emergency program has been implemented as a standard in the REG-DTM regulator. The operating principle can be described as follows: During undisturbed operation with the ∆Isinϕ and the ∆Isinϕ (S) procedures, the cosϕ...

Authors Figure 9 The user interface of the REGSim simulation software with three transformers connected in parallel In Figure 10, for example, the transformers T1 and T3 are operating on busbar a, while transformer T2 is feeding on busbar b. With the aid of the ParaGramer, it is also possible to depict high voltage busbars. The ParaGramer is thus a suitable tool for reliably implementing the most varied parallel connections with only minimum effort. Dipl.-Ing. (FH) Werner Haussel (graduate engineer of a university of applied sciences) Director Quality Management A. Eberle GmbH & Co. KG Figure...

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