Grounding transformers are most frequently — but not exclusively — used in the renewable industry to provide a relatively low-impedance path to ground in case of surges. This allows for safe maintenance of the grid without fear of damaging the electrical infrastructure. If the grounding transformer is connected to a feeder, special considerations are required to set the protection to …
The overall differential protection for a generator step-up transformer (GSU) began to trip when the generator was synced to the plant switchyard. Figure 1 shows the one-line diagram for the overall differential protection. There is one set of current transformers (CTs) on the high side of the GSU, one set of CTs on the low side of the GSU not …
This article demonstrates how to use numerical generator protection relay profile capability to measure the stator ground capacitance of a large combustion turbine generator. The measurements are taken when the generator is on-line and running at full speed while the generator breaker is open (no load), and again during startup as the exported power increases. The stator capacitance-to-ground (Figure 1) …
A large steam turbine generator tripped on 87 phase differential protection while attempting to synch the machine to the grid. However, only the main generator protection relay operated — not the backup protection. The goal of the analysis is to determine why only one relay operated and what caused the trip to occur. EVENT ANALYSIS Figure 1 shows the system …
The purpose of the sync check function (25) is to ensure that the voltage magnitude, phase angle, and frequency of the generator (VX) and the utility system (VS) are within a set of acceptable limits before the generator is synchronized with the system via closing the circuit breaker that connects them (Figure 1). An improper sync can result in electrical …
Generator faults are usually serious and can lead to significant repair costs and long outage times. PART I: ANALYSIS Part 1 demonstrates how to analyze a stator ground fault for a large combustion turbine generator. The faulted phase and fault location are determined using fault voltage recorded by the numerical generator protection relay installed for this generator. This information is …
This article analyzes several protection operations for large combustion turbine generators. Generator protection trips tend to be rare, so any major event is always of interest. EVENT 1: CLOSE-IN THREE-PHASE FAULT A large gas combustion turbine generator experienced a close-in three-phase fault during a rainstorm. The generator terminal voltage is rated 13.8 kV line-to-line, and the machine is high-impedance grounded. The …
Numerical protection relays offer the ability to alarm for many abnormal operating conditions, including the health of the relay. Below is a list of typical conditions to alarm for due to an abnormal condition: Overexcitation Phase undervoltage Loss of potential or blown fuse(s) Relay firmware or hardware failure Relay access Over or under station battery DC voltage Trip coil monitoring …
Historically, CT connections compensated for the phase shift across a transformer when applying differential protection prior to the advent of numerical transformer protection relays. For example, a delta-wye transformer would have wye connected CTs on the delta side and delta connected CTs on the wye side. The delta connected CTs have the same connection as the transformer delta connected winding …
Multi-function numerical generator protection relays can calculate the insulation resistance of a synchronous generator field winding to ground. The calculation can be performed on an energized or de-energized generator. The particular relay discussed in this article uses a separate module located close to the rotor slip rings and brushes to monitor the field. The close proximity of the module to …