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Interlocking table and CILO equation generator
Choose the substation configuration and get the interlocking matrix per device, the EnaOpn and EnaCls equations of the CILO node, which conditions are bay-level and which are station-level, and the list of FAT and SAT test cases. It comes from the same model as the switching simulator.
IEC 61850-7-4CILO, CSWI, XSWI and XCBRIEC 61850-7-3Dbpos position and qualityIEC 62271-102interlocking of disconnectors and earthing switchesIEC 61936-1interlocking
Results
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Assumptions
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Charts
- Positions one bay publishes for another (number of devices)
Calculation and details
CILO equations
IEC 61850-7-4 notation: ∧ = and, ∨ = or. A term holds only with the device in that end position and good quality; in an intermediate (Dbpos 00) or bad (11) position, or with invalid quality, it counts as not met and the command is blocked.
Underlined = station term (another bay). Italics = remote end of the line.
Interlocking matrix
O = open, C = closed, N = protection on its own breaker, T = protection transferred; the superscript is the alternative; * = one of the marked terms in the same alternative is enough; — = not involved. Columns with a yellow border: devices of another bay.
Subscriptions between bays
What it means for your project
FAT and SAT test cases
One case per alternative with all its conditions met and one per negated condition. Devices that do not appear in the initial state are not involved in the interlocking. Repeat each blocked case with the device in an intermediate or bad position and with the GOOSE signal lost: it must stay blocked.
| N.º | Order | Case | Initial state | Expected | Result |
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Choose the substation configuration and get the interlocking matrix per device, the EnaOpn and EnaCls equations of the CILO node, which conditions are bay-level and which are station-level, and the list of FAT and SAT test cases. It comes from the same model as the switching simulator.
IEC 61850-7-4CILO, CSWI, XSWI and XCBRIEC 61850-7-3Dbpos position and qualityIEC 62271-102interlocking of disconnectors and earthing switchesIEC 61936-1interlocking
What it is for
To write or review the interlocking logic of the bay controllers before configuring them, to prepare the FAT and SAT test protocol, and to know which positions each bay has to exchange with the others. The table comes from the same model as the switching simulator: what the equation allows is exactly what the simulator lets you operate.
How it is generated
IEC 61850-7-4CILO: EnaOpn and EnaClsIEC 61850-7-3Dbpos
EnaCls = (t₁₁ ∧ t₁₂ ∧ …) ∨ (t₂₁ ∧ t₂₂ ∧ …) ∨ …
- Sum of products: each alternative is a product (AND) of position conditions, and one alternative is enough to enable the command. A term with options (x open ∨ y open) is written in brackets.
- Fail safe: an intermediate (00) or bad (11) Dbpos position, or any quality other than good, satisfies no term. A damaged auxiliary contact or a lost GOOSE therefore blocks the command instead of enabling it.
IEC 62271-102disconnectors and earthing switchesEN 50110-1five golden rulesIEC 61936-1interlocking
- Conditions: those of the switching simulator of each configuration, with their source rule: disconnectors that only operate with the breaker open or with a parallel path, earthing switches that only close on an isolated section, breakers that do not close onto an earth, and the coupler that does not open while a bay joins both busbars.
- Bay or station: a term is a station term when it names a device of another bay or of the busbars. Each distinct device a bay needs is a subscription to the position (XCBR.Pos or XSWI.Pos) published by the controller that owns that device; the publishers give the number of datasets.
- Test cases: for each alternative, one case with all its terms true and one per negated term, with the other positions chosen so that no other alternative enables the command.
- Validation: every equation is compared, state by state, with what the simulator engine accepts and rejects, in every configuration.
IEC 81346-2letters QA, QB, QC
- IEC 81346 names: QA for the circuit breaker, QB for disconnectors and switch-disconnectors, QC for earthing switches. The number after the letters is set by each project; here it is the order of the device inside its bay (Tiza convention).
The alert on the station-term indicator is a Tiza criterion: with hard-wired station interlocking and more than two busbars, the number of contacts between bays grows with every extension, and GOOSE or the station controller logic should be considered.
Limits of the table
- It is a typical bay of the simulator, with its number of bays; the real project is defined by its engineering and the manufacturer's drawings.
- It only covers the electrical command interlocking (CILO). It does not include mechanical interlocks, key locks, the internal interlocks of medium-voltage switchgear or local control in the yard.
- It does not include command permissives that are not interlocking: synchronism check (25), SF6 pressure, spring not charged, local or remote selector.
- The conditions at the remote end of a line are coordinated with the other substation.
- Some projects allow an interlocking override with a key and a procedure; the table does not model it.
Frequently asked questions
What is the CILO logical node in IEC 61850?
CILO is the interlocking logical node of IEC 61850-7-4. It computes two permissions per device, EnaOpn (enabled to open) and EnaCls (enabled to close), from the positions of its own devices and of other bays. The control node CSWI checks them before executing a command: if the permission is false, the command is rejected.
What is the difference between bay and station interlocking?
Bay interlocking only uses devices of the same bay, such as the breaker earthing switches, and the controller of that bay solves it with its own inputs. Station interlocking needs the position of devices of other bays, such as the coupler or the busbar earthing switch, which arrives by GOOSE, through the station controller logic or by hard-wired contacts.
How is interlocking logic tested in FAT and SAT?
For each alternative of each equation, one case is checked in which all conditions are met (command enabled) and one case for each missing condition (command blocked). The blocked cases are repeated with the device in an intermediate or bad position and with the GOOSE signal lost: in all of them it must stay blocked.
We configure and test your interlocking
We write the interlocking logic in your bay controllers, configure the GOOSE messages between bays and run the whole matrix in FAT and SAT, recording every condition.