Schweitzer Engineering Laboratories

The present disclosure pertains to systems and methods for protecting multi-phase wound-rotor electric machines in an electric power delivery system. Protection of these machines uses an equivalent rotor current determined using rotor current signals, and an equivalent stator current determined using stator current signals. The equivalent rotor and stator currents are independent of the voltage and rotor position signals and are used in protection elements to determine a fault condition.

Quotient differential protection of a dual-core phase shifting transformer (130) is described herein. Load-side currents and source-side currents are used without need of tap changer and control switch positions of the dual-core phase-shifting transformer being protected. The quotient differential signal is determined based on comparing the winding turn ratios in individual transformer phases, resulting in a differential signal that includes the products of currents. Similarly, the restraining signal comprises the products of currents. Fig. 1

In various examples, a host HSR device determines bidirectional latency values in an HSR ring without adding network traffic beyond the supervision frames mandated by the HSR protocol. The host HSR device receives its own supervision frames after the frames traverse the ring in both clockwise and counterclockwise directions. The host HSR device determines direction-specific roundtrip latency values, which are transmitted and used to, for example, set channel delay parameters in protective relays, assert alarms when latency or frame-return timeout thresholds are exceeded, and/or take other protective or reporting actions. In some examples, the larger of the two latency values is used to calculate a maximum roundtrip latency, which can be used to adjust or set a channel delay setting of a protective relay to ensure that the protective relay will continue to operate with the ring in a degraded state.

Fault location determination using local and remote incremental voltages and replica currents is disclosed herein. Using the observation that the change in voltage at the fault location estimated from a local terminal is the same as the change in voltage at the fault location estimated from a remote terminal, the embodiments herein determine fault location by minimizing a difference between a change-in-voltage at the fault location estimated using the local incremental voltages and replica currents and a change-in-voltage at the fault location estimated using the remote incremental voltages and replica currents.

A system includes a first intelligent electronic device (IED) (202) of an electric power delivery system (200). The first IED (202) may measure a local current and a local voltage (206), transmit a first signal indicative of the local current and voltage measurements to additional IEDs (204) via one or more communication channels, receive one or more additional signals indicative of remote current and voltage measurements (210) from each of the additional IEDs (206), determine a respective asymmetry of each of the communication channels based on the local current and voltage measurements (206) and the remote current and voltage measurements (210), determine a total asymmetry based on the respective asymmetries, compare the total asymmetry to one or more threshold relationships between operating currents and restraining currents, each of the one or more threshold relationships comprising a slope value, and perform a control function based on the comparison.

Systems and methods for determining primary and failover paths in a programmable communication network are disclosed herein. In one embodiment, a system to identify a plurality of communication paths may operate in conjunction with a programmable communication network connecting a source and a destination. A path discovery subsystem may discover both a first and a second completed communication path between the source and the destination. A cost calculation subsystem may calculate a first cost for the first completed communication path and a second cost for the second completed communication path. A routing subsystem may identify a primary communication path based on the first cost and the second cost, and program the plurality of nodes to implement the primary communication path.

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