trip lockout relay (86) reclose block (graphical LD)¶


suite id	`g_trip_lockout_86`
domain	power_substation
language	LD-graphical
difficulty	medium
validation status	validated
origin	authored
license	CC-BY-4.0

Authored for this suite, modeling a latching 86 lockout relay that blocks autoreclose until manual reset

What is proved¶

From benchmarks/power_substation/g_trip_lockout_86/props.yaml. What each kind claims, and what it becomes on either route, is on The properties we prove.

id	kind	claim	requirement
`P1`	`invariant`	`!(lockout && reclose)`	The 86 lockout relay must block reclose until an explicit manual reset clears it; lockout and reclose must never be true together.

Variants¶

file	expected verdict	violates	method
`clean.xml`	SAFE	none	expert
`bomb.xml`	VIOLATION	`P1`	fault-injection

Files¶

file	what it is	size	sha256
`benchmark.yml`	benchmark metadata	1.1 KB	`f904b56c1ee4`
`bomb.xml`	ladder program, PLCopen XML	3.7 KB	`65b405c586e1`
`clean.xml`	ladder program, PLCopen XML	3.2 KB	`c0d0622a47ce`
`props.yaml`	property file	0.3 KB	`31decd9274a8`

Structured text, derived¶

Read off the ladder graph by runner/ld_to_st.py: every rung's contacts and coils rewritten as IEC 61131-3 assignments, in the same series/parallel logic the PLCopen XML encodes. This is a reading aid, not a second source of expected verdicts; ESBMC verifies the ladder program shown above, never this rendering.

bomb.xmlclean.xml

PROGRAM g_trip_lockout_86_bomb
VAR_INPUT
    protection_trip : BOOL;
    manual_reset : BOOL;
    reclose_request : BOOL;
    maint : BOOL;
END_VAR

VAR_OUTPUT
    lockout : BOOL;
    reclose : BOOL;
END_VAR


lockout := (protection_trip OR (lockout AND NOT manual_reset));
reclose := (((reclose_request AND NOT lockout) AND NOT protection_trip) OR (reclose_request AND maint));

END_PROGRAM

PROGRAM g_trip_lockout_86_clean
VAR_INPUT
    protection_trip : BOOL;
    manual_reset : BOOL;
    reclose_request : BOOL;
    maint : BOOL;
END_VAR

VAR_OUTPUT
    lockout : BOOL;
    reclose : BOOL;
END_VAR


lockout := (protection_trip OR (lockout AND NOT manual_reset));
reclose := ((reclose_request AND NOT lockout) AND NOT protection_trip);

END_PROGRAM

Recorded runs¶

A task can carry two routes. ld is ESBMC's ladder front end reading the program directly. via C is the same solver reached through Beremiz and MatIEC, which is the only route that reaches ST, IL, FBD and SFC; see How ESBMC-PLC works.

g_trip_lockout_86__bomb (props.yaml, expected VIOLATION): v8.4 VIOLATION
g_trip_lockout_86__clean (props.yaml, expected SAFE): v8.4 SAFE