NERC TRANSMISSION OPERATOR (TOP) Actual
SYSTEM OPERATIONS EXAM – Complete
Solutions | Verified Review Guide
SECTION 1: Real-Time Transmission System Operations (Q1-25)
Q1: As the TOP, your Real-Time Assessment tool indicates a transmission line is loaded
to 104% of its System Operating Limit (SOL). The Reliability Coordinator (RC) has not yet
called. Your immediate and mandatory action is to:
A) Initiate the Transmission Loading Relief (TLR) procedure.
B) Take immediate operational actions to return the facility to within its SOL and notify
the RC.
C) Notify the RC and wait for a directive.
D) Shed load to reduce the overload.
Correct Answer: B
COMPLETE SOLUTION (TOP Debrief):
● Situational Awareness: An SOL violation is an immediate threat to the
transmission system you operate. The TOP has the primary responsibility to keep
facilities within limits.
● Rule/Guideline: NERC Standard TOP-001-5, Requirement R2: "The Transmission
Operator shall operate… within all… SOLs." It further requires taking "immediate
action" to mitigate and notifying the RC.
● Action Sequence Justification: The TOP must act first to protect the system
using available real-time controls (e.g., re-dispatch, reconfiguration). Concurrently
or immediately after acting, the RC must be notified. Waiting (C) violates the
"immediate action" requirement. TLR (A) is a specific, formal process for broader
coordination, not the first action for a simple SOL violation. Load shedding (D) is
an extreme measure typically requiring an RC or BA directive.
● Post-Mortem:
○ A) Incorrect Procedure. TLR is initiated by the TSP/RC for wider market
coordination, not the TOP's first real-time mitigation step.
, ○ C) Passive/Non-Compliant. Waiting violates TOP-001 R2's "immediate
action" mandate.
○ D) Beyond Scope/Authority. The TOP does not typically have the authority
to independently shed customer load for an SOL; that is a BA/RC action.
Q2: You are the TOP on shift. Your RC issues a verbal directive: "Immediately reduce
loading on Line 345-1 to below 90% of SOL to prevent IROL violation." Line 345-1 is
currently at 98% SOL. You have capacitor banks and reactor banks available. Which
action sequence complies with IRO-009 and TOP-001?
A) Request the RC to issue the directive to the BA instead; you cannot control line
loading.
B) Immediately switch in a series capacitor to reduce line impedance.
C) Open the line to de-energize it completely, eliminating the overload.
D) Immediately reconfigure flows or request generation redispatch from the BA to
reduce loading, then confirm compliance to the RC.
Correct Answer: D
COMPLETE SOLUTION (TOP Debrief):
● Situational Awareness: You have received a binding RC directive regarding an
IROL. This is a directive to the TOP to take action, often involving coordination
with the BA for generation redispatch or using transmission switching.
● Rule/Guideline: IRO-009-3, Requirement R2: The TOP must comply with RC
directives. TOP-001-5, Requirement R6: The TOP must have protocols for
operating instructions.
● Action Sequence Justification: The TOP must act to comply. This involves either
direct transmission switching (if available and safe) or coordinating with the BA
(who controls generation) to redispatch. The TOP facilitates this reduction.
Simply opening the line (C) is unacceptable as it removes the path entirely.
Requesting the RC redirect (A) improperly deflects a TOP-targeted directive.
● Post-Mortem:
○ A) Authority Confusion. The directive was issued to the TOP; deflecting it
violates IRO-009 compliance obligations.
○ B) Technical Error. Series capacitors reduce impedance and typically
increase power flow (inverse to impedance), potentially worsening the
overload.
, ○ C) Overcorrection. Opening the line violates the continuity of service
principle and N-1 security; it is not a valid response to an overload
warning.
Q3: You are clearing a switching order to de-energize a 138 kV line for maintenance.
Your SCADA shows the breaker is open, but the disconnect switches (isolators) are
closed. The switches are not motor-operated and require manual operation in the field.
What is your next step per TOP-001 safe operating practices?
A) Proceed to issue the switching order to open the field switches; the breaker status is
sufficient isolation.
B) Place a "Hold" on the order and verify with field personnel that visual confirmation of
isolation is possible before proceeding.
C) Cancel the outage and tell the maintenance crew to come back tomorrow.
D) Assume the SCADA is wrong and the line is already de-energized.
Correct Answer: B
COMPLETE SOLUTION (TOP Debrief):
● Situational Awareness: You are preparing a clearance for maintenance. The
breaker is open, providing electrical isolation from the source, but the visible
isolation (disconnects) is not yet achieved. Safety requires confirmed visible
isolation.
● Rule/Guideline: TOP-001-5, Requirement R5: The TOP shall issue operating
instructions that include verification of switching. Safe operating practice
requires visible isolation (or confirmation thereof) before clearance is granted.
● Action Sequence Justification: Before personnel can work on the line, isolation
must be verified. Since switches are manual, you must coordinate with field
crews to confirm the open position. Placing a hold maintains safety while
verification occurs.
● Post-Mortem:
○ A) Unsafe Assumption. Issuing the order without confirming field
conditions risks personnel safety if the breaker is leaking voltage or if the
switches cannot be visually confirmed.
○ C) Unnecessary Cancellation. There is no indication the outage cannot
proceed, only that verification is needed.
○ D) Dangerous Assumption. Assuming SCADA is wrong without verification
is reckless.
, Q4: Your SCADA indicates a voltage violation at Substation X: 132 kV on a 138 kV bus
(0.957 pu). You have shunt capacitor banks available at the substation. Your first action
is to:
A) Immediately call the RC to declare an emergency.
B) Switch in the available shunt capacitor banks to boost voltage.
C) Request the BA to increase generation at the nearest plant.
D) Block tap changers on transformers serving the load.
Correct Answer: B
COMPLETE SOLUTION (TOP Debrief):
● Situational Awareness: Low voltage at a transmission bus. The TOP has local
reactive resources (capacitors) available to correct this.
● Rule/Guideline: TOP-001-5, Requirement R4: The TOP shall operate the
transmission system within voltage limits. VAR-001 (Voltage and Reactive
Control) requires use of available reactive resources.
● Action Sequence Justification: The TOP has direct control over substation
equipment including shunt capacitors. This is the fastest, most direct response.
The RC (A) should be notified of actions taken or if resources are insufficient, but
the TOP acts first. Generation (C) is a BA/RC coordination step. LTC blocking (D)
prevents further voltage drop but does not correct the current violation.
● Post-Mortem:
○ A) Overreaction/Delay. Declaring an emergency before using available
local resources is inefficient and may violate the self-sufficiency principle
of TOP operations.
○ C) Indirect/Slow. Generation adjustments take minutes; capacitor
switching is instantaneous.
○ D) Symptomatic Only. Blocking LTCs stops the bleeding but doesn't
transfuse blood.
Q5: A severe storm is approaching. Your Real-Time Assessment indicates that if a
specific 230 kV line trips (N-1), a parallel line will exceed its SOL at 110%. This is a
potential post-contingency violation. Your action per TOP-002 is to:
A) Take no action; the violation hasn't happened yet.
B) Immediately open the parallel line to prevent the overload.
C) Initiate pre-contingency mitigation (e.g., reconfiguration or requesting redispatch) to
relieve the potential overload.
D) Wait for the line to actually trip before responding.
SYSTEM OPERATIONS EXAM – Complete
Solutions | Verified Review Guide
SECTION 1: Real-Time Transmission System Operations (Q1-25)
Q1: As the TOP, your Real-Time Assessment tool indicates a transmission line is loaded
to 104% of its System Operating Limit (SOL). The Reliability Coordinator (RC) has not yet
called. Your immediate and mandatory action is to:
A) Initiate the Transmission Loading Relief (TLR) procedure.
B) Take immediate operational actions to return the facility to within its SOL and notify
the RC.
C) Notify the RC and wait for a directive.
D) Shed load to reduce the overload.
Correct Answer: B
COMPLETE SOLUTION (TOP Debrief):
● Situational Awareness: An SOL violation is an immediate threat to the
transmission system you operate. The TOP has the primary responsibility to keep
facilities within limits.
● Rule/Guideline: NERC Standard TOP-001-5, Requirement R2: "The Transmission
Operator shall operate… within all… SOLs." It further requires taking "immediate
action" to mitigate and notifying the RC.
● Action Sequence Justification: The TOP must act first to protect the system
using available real-time controls (e.g., re-dispatch, reconfiguration). Concurrently
or immediately after acting, the RC must be notified. Waiting (C) violates the
"immediate action" requirement. TLR (A) is a specific, formal process for broader
coordination, not the first action for a simple SOL violation. Load shedding (D) is
an extreme measure typically requiring an RC or BA directive.
● Post-Mortem:
○ A) Incorrect Procedure. TLR is initiated by the TSP/RC for wider market
coordination, not the TOP's first real-time mitigation step.
, ○ C) Passive/Non-Compliant. Waiting violates TOP-001 R2's "immediate
action" mandate.
○ D) Beyond Scope/Authority. The TOP does not typically have the authority
to independently shed customer load for an SOL; that is a BA/RC action.
Q2: You are the TOP on shift. Your RC issues a verbal directive: "Immediately reduce
loading on Line 345-1 to below 90% of SOL to prevent IROL violation." Line 345-1 is
currently at 98% SOL. You have capacitor banks and reactor banks available. Which
action sequence complies with IRO-009 and TOP-001?
A) Request the RC to issue the directive to the BA instead; you cannot control line
loading.
B) Immediately switch in a series capacitor to reduce line impedance.
C) Open the line to de-energize it completely, eliminating the overload.
D) Immediately reconfigure flows or request generation redispatch from the BA to
reduce loading, then confirm compliance to the RC.
Correct Answer: D
COMPLETE SOLUTION (TOP Debrief):
● Situational Awareness: You have received a binding RC directive regarding an
IROL. This is a directive to the TOP to take action, often involving coordination
with the BA for generation redispatch or using transmission switching.
● Rule/Guideline: IRO-009-3, Requirement R2: The TOP must comply with RC
directives. TOP-001-5, Requirement R6: The TOP must have protocols for
operating instructions.
● Action Sequence Justification: The TOP must act to comply. This involves either
direct transmission switching (if available and safe) or coordinating with the BA
(who controls generation) to redispatch. The TOP facilitates this reduction.
Simply opening the line (C) is unacceptable as it removes the path entirely.
Requesting the RC redirect (A) improperly deflects a TOP-targeted directive.
● Post-Mortem:
○ A) Authority Confusion. The directive was issued to the TOP; deflecting it
violates IRO-009 compliance obligations.
○ B) Technical Error. Series capacitors reduce impedance and typically
increase power flow (inverse to impedance), potentially worsening the
overload.
, ○ C) Overcorrection. Opening the line violates the continuity of service
principle and N-1 security; it is not a valid response to an overload
warning.
Q3: You are clearing a switching order to de-energize a 138 kV line for maintenance.
Your SCADA shows the breaker is open, but the disconnect switches (isolators) are
closed. The switches are not motor-operated and require manual operation in the field.
What is your next step per TOP-001 safe operating practices?
A) Proceed to issue the switching order to open the field switches; the breaker status is
sufficient isolation.
B) Place a "Hold" on the order and verify with field personnel that visual confirmation of
isolation is possible before proceeding.
C) Cancel the outage and tell the maintenance crew to come back tomorrow.
D) Assume the SCADA is wrong and the line is already de-energized.
Correct Answer: B
COMPLETE SOLUTION (TOP Debrief):
● Situational Awareness: You are preparing a clearance for maintenance. The
breaker is open, providing electrical isolation from the source, but the visible
isolation (disconnects) is not yet achieved. Safety requires confirmed visible
isolation.
● Rule/Guideline: TOP-001-5, Requirement R5: The TOP shall issue operating
instructions that include verification of switching. Safe operating practice
requires visible isolation (or confirmation thereof) before clearance is granted.
● Action Sequence Justification: Before personnel can work on the line, isolation
must be verified. Since switches are manual, you must coordinate with field
crews to confirm the open position. Placing a hold maintains safety while
verification occurs.
● Post-Mortem:
○ A) Unsafe Assumption. Issuing the order without confirming field
conditions risks personnel safety if the breaker is leaking voltage or if the
switches cannot be visually confirmed.
○ C) Unnecessary Cancellation. There is no indication the outage cannot
proceed, only that verification is needed.
○ D) Dangerous Assumption. Assuming SCADA is wrong without verification
is reckless.
, Q4: Your SCADA indicates a voltage violation at Substation X: 132 kV on a 138 kV bus
(0.957 pu). You have shunt capacitor banks available at the substation. Your first action
is to:
A) Immediately call the RC to declare an emergency.
B) Switch in the available shunt capacitor banks to boost voltage.
C) Request the BA to increase generation at the nearest plant.
D) Block tap changers on transformers serving the load.
Correct Answer: B
COMPLETE SOLUTION (TOP Debrief):
● Situational Awareness: Low voltage at a transmission bus. The TOP has local
reactive resources (capacitors) available to correct this.
● Rule/Guideline: TOP-001-5, Requirement R4: The TOP shall operate the
transmission system within voltage limits. VAR-001 (Voltage and Reactive
Control) requires use of available reactive resources.
● Action Sequence Justification: The TOP has direct control over substation
equipment including shunt capacitors. This is the fastest, most direct response.
The RC (A) should be notified of actions taken or if resources are insufficient, but
the TOP acts first. Generation (C) is a BA/RC coordination step. LTC blocking (D)
prevents further voltage drop but does not correct the current violation.
● Post-Mortem:
○ A) Overreaction/Delay. Declaring an emergency before using available
local resources is inefficient and may violate the self-sufficiency principle
of TOP operations.
○ C) Indirect/Slow. Generation adjustments take minutes; capacitor
switching is instantaneous.
○ D) Symptomatic Only. Blocking LTCs stops the bleeding but doesn't
transfuse blood.
Q5: A severe storm is approaching. Your Real-Time Assessment indicates that if a
specific 230 kV line trips (N-1), a parallel line will exceed its SOL at 110%. This is a
potential post-contingency violation. Your action per TOP-002 is to:
A) Take no action; the violation hasn't happened yet.
B) Immediately open the parallel line to prevent the overload.
C) Initiate pre-contingency mitigation (e.g., reconfiguration or requesting redispatch) to
relieve the potential overload.
D) Wait for the line to actually trip before responding.
