Introduction; Power System Requirements; Microtapp Functionality; Inputs - Siemens 7sg15 microtapp Operation Manual

1

Introduction

The MicroTAPP voltage control and monitor system is an advanced numeric system based on the widely used
SuperTAPP relay. The operational requirements for efficient control of tap changing transformers and protection
against abnormal voltage levels is provided in a compact and user friendly design contained within a standard
Epsilon case of 4U (177mm) in height and E8 (208mm) or E12 (312mm) in width. The case size selected
depends upon the input/output requirements of the scheme connections. Advanced features of metering, data
storage and communications for remote control and data transfer are included as standard with the relay.
Full supervision and self-monitoring of the internal relay functions give a high operational reliability and the
modular construction allows for on-site serviceability.
A standard, comprehensive menu-based interface gives user-friendly access to the relay settings, display options
and fault data. A communications port is provided for local connection to a laptop PC and two fibre optic ports for
remote connection. A Reydisp Evolution software package is used to set and commission the relay.
2

Power system requirements

An important aspect of supply quality is the correct application of voltage levels to all transmission and distribution
networks. With a growing amount of embedded generation, both synchronous and asynchronous generator types
are now becoming relatively common within distribution systems. The control of voltage levels require systems
that can function under dynamic operating regimes. This need, coupled with growing customer expectation and
use of sophisticated electrical equipment such as computers and thyristor controlled machinery puts an added
responsibility upon the supplier of electrical energy to ensure that the delivered level and quality of supply is
always within the parameters set down by regulatory bodies.
Automatic voltage control of the electrical network is implemented by use of voltage sensing relays which control
motorised On Load Tap Changers (OLTC), for distribution system these devices are normally not economic below
a transformer secondary voltage of 11kV or 6.6kV. The complexity of these systems and the mechanical nature of
the OLTC contribute to the long term unreliability and danger of abnormal voltages being applied to the
distribution system. The main problem areas with traditional schemes are: -
• Complex control circuitry associated with the parallel operation of transformers in a substation
•
Operational limitations when networks are operated in parallel
•
Inadequate performance under varying load conditions
• A high skill requirement for installation, operation and maintenance
The MicroTAPP system overcomes these historical problems associated with voltage control.
3

MicroTAPP Functionality

The overall functionality of the MicroTAPP can be understood by reference to Figure 1. Analogue quantities of
voltage and current are connected to the measurement inputs. These quantities are filtered for noise, sampled at
32 times per cycle (for a 50Hz system) and digitised. The rate of sampling enables the stored waveform data to
be used by the relay for measurement and supply quality analysis.
A separate input voltage is connected to the voltage monitor input and treated in the same way as for the
measurement input but by discrete and separate algorithms. The connections to the relay allow for use with a 3
phase VT, one phase is used for measurement, one for level checking and the 3 phase connection for
determination of voltage quality (NPS content). Where a single phase VT is used the measurement and monitor
inputs are connected together.
3.1

Inputs

Plant inputs such as 'tap in progress' and remote 'tap raise or lower' are connected to status inputs and allocated
for function in the input matrix, accessible from relay menu system. The tap change position is also connected to
the relay for the purpose of 'intelligent' operation monitoring, the action of which is described in the protection
section of this document. As a standard the following types of tap position sender are possible; Resistor chain,
Binary Coded Decimal (BCD), True binary and Gray Code.
©2013 Siemens Protection Devices Limited
7SG15 MicroTAPP Description of Operation
Chapter 1 Page 4 of 38