Reliability Standard BAL-004-WECC-3

BAL-004-WECC-3 ─ Automatic Time Error Correction
A. Introduction
1. Title:

Automatic Time Error Correction

2. Number:

BAL-004-WECC-3

3. Purpose:
To maintain Interconnection frequency and to ensure that Time Error
Corrections and Primary Inadvertent Interchange (PII) payback are effectively conducted
in a manner that does not adversely affect the reliability of the Interconnection.
4. Applicability
4.1. Functional Entities
4.1.1

Balancing Authorities that operate synchronously in the Western
Interconnection.

5. Effective Date:
On the first day of the second quarter, after applicable regulatory
approval has been received (or the Reliability Standard otherwise becomes effective the
first day of the fourth quarter following NERC Board adoption where regulatory
approval is not required).
B. Requirements and Measures
R1. Each Balancing Authority shall operate its system such that, following the conclusion of
each month, the month-end absolute value of its On-Peak and Off-Peak, Accumulated
Primary Inadvertent Interchange (PIIaccum), as calculated by the WECC Interchange Tool
(WIT) or its successor electronic confirmation tool, are each individually less than or
equal to: [Violation Risk Factor Medium:] [Time Horizon: Operations Assessment]
1.1 For load-serving Balancing Authorities, 150% of the previous calendar year’s
integrated hourly Peak Demand,
1.2 For generation-only Balancing Authorities, 150% of the previous calendar year’s
integrated hourly peak generation.
M1. Each Balancing Authority will have evidence that it operated its system such that,
following the conclusion of each month, the month-end absolute value of its OnPeak and Off-Peak, Accumulated Primary Inadvertent Interchange (PIIaccum), as
calculated by the WECC Interchange Tool (WIT) or its successor electronic
confirmation tool, meets all criteria stated in Requirement R1.
R2. Each Balancing Authority shall, upon discovery of an error in the calculation of PIIhourly,
recalculate within 90 days, the value of PIIhourly and adjust the PIIaccum from the time of
the error. [Violation Risk Factor: Medium] [Time Horizon: Operations Assessment]
M2. Forms of acceptable evidence of compliance with Requirement R2 include but are
not limited to any one of the following:
Page 1 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
• Data, screen shots from the WECC Interchange Tool (WIT) or its successor electronic
confirmation tool,
• Data, screen shots from the internal Balancing Authority tool, or
• Production of data from any other databases, spreadsheets, displays.
R3. Each Balancing Authority shall keep its Automatic Time Error Correction (ATEC) in
service, with an allowable exception period of less than or equal to an accumulated 24
hours per calendar quarter for ATEC to be out of service. [Violation Risk Factor:
Medium] [Time Horizon: Same-day Operations]
M3. Forms of acceptable evidence of compliance with Requirement R3 may include,
but are not limited to:
•

Dated archived files,

•

Historical data,

•

Other data that demonstrates the ATEC was out of service for less than 24
hours per calendar quarter.

R4. Each Balancing Authority shall compute each of the following using the WECC
Interchange Tool (WIT) or its successor electronic confirmation tool, no later than 50
minutes after each hour,
4.1. PIIhourly,
4.2. PIIaccum,
4.3. Automatic Time Error Correction term (IATEC).
[Violation Risk Factor: Medium] [Time Horizon: Operations Assessment]
M4. Forms of acceptable evidence of compliance with Requirement R4 include but are
not limited to any one of the following:
•

Data, screen shots from the WECC Interchange Tool (WIT) or its
successor electronic confirmation tool, that demonstrate compliance;

•

Data, screen shots from internal Balancing Authority tool that demonstrate
compliance; or,

•

Data from any other databases, spreadsheets, displays that demonstrate
compliance.

R5. Each Balancing Authority shall be able to change its Automatic Generation Control
operating mode between Flat Frequency (for blackout restoration); Flat Tie Line
(for loss of frequency telemetry); Tie Line Bias; and Tie Line Bias plus Time Error
Control (used in ATEC mode), to correspond to current operating conditions.
[Violation Risk Factor: Medium] [Time Horizon: Real-Time Operations]
Page 2 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
M5. Forms of acceptable evidence of compliance with Requirement R5 include but
are not limited to any one of the following:
• Screen shots from Energy Management System,
• Demonstration using an off-line system.
R6. Each Balancing Authority shall recalculate the PIIhourly and PIIaccum for the On-Peak
and Off-Peak periods whenever adjustments are made to hourly Inadvertent
Interchange or ∆TE. [Violation Risk Factor: Medium] [Time Horizon: Operations
Assessment]
M6. Forms of acceptable evidence of compliance with Requirement R6 include but
are not limited to any one of the following:
• Data, screen shots from the WECC Interchange Tool (WIT) or its
successor electronic confirmation tool, that demonstrate compliance;
• Data, screen shots from an internal Balancing Authority tool that
demonstrate compliance with; or,
• Data from any other databases, spreadsheets, displays that demonstrate
compliance.
R7. Each Balancing Authority shall make the same adjustment to the PIIaccum as it did for
any month-end meter reading adjustments to Inadvertent Interchange. [Violation Risk
Factor: Medium] [Time Horizon: Operations Assessment]
M7. Forms of acceptable evidence of compliance with Requirement R7 include but are
not limited to any one of the following:
• Data, screen shots from the WECC Interchange Tool (WIT) or its
successor electronic confirmation tool, that demonstrate compliance;
• Data, screen shots from an internal Balancing Authority tool that
demonstrate compliance; or,
• Production of data from any other databases, spreadsheets, displays that
demonstrate compliance.
R8. Each Balancing Authority shall payback Inadvertent Interchange using ATEC rather
than bilateral and unilateral payback. [Violation Risk Factor: Medium] [Time Horizon:
Operations Assessment]
M8. Forms of acceptable evidence of compliance with Requirement R8 include but are
not limited to historical On-Peak and Off-Peak Inadvertent Interchange data, data
from the WECC Interchange Tool, and ACE data.

Page 3 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
C. Compliance
1. Compliance Monitoring Process
1.1 Compliance Enforcement Authority
The Regional Entity shall serve as the Compliance Enforcement Authority.
For entities that do not work for the Regional Entity, the Regional Entity shall serve
as the Compliance Enforcement Authority.
For Reliability Coordinators and other functional entities that work for their
Regional Entity, the ERO or a Regional Entity approved by the ERO and FERC or
other applicable governmental authorities shall serve as the Compliance
Enforcement Authority.
For responsible entities that are also Regional Entities, the ERO or a Regional Entity
approved by the ERO and FERC or other applicable governmental authorities shall
serve as the Compliance Enforcement Authority.
1.2 Compliance Monitoring and Assessment Processes:
Compliance Audits
Self-Certifications
Spot Checking
Compliance Investigations
Self-Reporting
Complaints
1.3

Evidence Retention
The following evidence retention periods identify the period of time an entity is
required to retain specific evidence to demonstrate compliance. For instances
where the evidence retention period specified below is shorter than the time since
the last audit, the Compliance Enforcement Authority may ask an entity to provide
other evidence to show that it was compliant for the full time period since the last
audit.
Each Balancing Authority in the Western Interconnection shall retain the values of
PIIhourly, PIIaccum (On-Peak and Off-Peak), ∆TE and any month-end adjustments for
the preceding calendar year (January – December), as well as the current calendar
year.
Each Balancing Authority in the Western Interconnection shall retain the amount of
time the Balancing Authority operated without ATEC for the preceding calendar
year (January – December), as well as the current calendar year.

1.4

Additional Compliance Information
None
Page 4 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
Table of Compliance Elements

R#

Time
Horizon

VRF

Violation Severity Levels
Lower VSL

Moderate VSL

High VSL

Severe VSL

R1

Operations
Assessment

Medium

Following the
conclusion of each
month each Balancing
Authority’s absolute
value of PIIaccum for
either the On-Peak
period or Off-Peak
period exceeded
150%, but was less
than or equal to 160%
of the previous
calendar year’s Peak
Demand or peak
generation for
generation-only
Balancing Authorities.

Following the
conclusion of each
month each Balancing
Authority’s absolute
value of PIIaccum for
either the On-Peak
period or Off-Peak
period exceeded
160%, but was less
than or equal to 170%
of the previous
calendar year’s Peak
Demand or peak
generation for
generation-only
Balancing Authorities.

Following the
conclusion of each
month each Balancing
Authority’s absolute
value of PIIaccum for
either the On-Peak
period or Off-Peak
period exceeded
170%, but was less
than or equal to 180%
of the previous
calendar year’s Peak
Demand or peak
generation for
generation-only
Balancing Authorities.

Following the
conclusion of each
month each Balancing
Authority’s absolute
value of PIIaccum for
either the On-Peak
period or Off-Peak
period exceeded 180%
of the previous
calendar year’s Peak
Demand or peak
generation for
generation-only
Balancing Authorities.

R2

Operations
Assessment

Medium

The Balancing
Authority did not
recalculate PIIhourly
and adjust the PIIaccum
within 90 days of the
discovery of the error;
but made the
required
recalculations and
adjustments within
120 days.

The Balancing
Authority did not
recalculate PIIhourly and
adjust the PIIaccum
within 120 days of the
discovery of the error;
but made the required
recalculations and
adjustments within
150 days.

The Balancing
Authority did not
recalculate PIIhourly and
adjust the PIIaccum
within 150 days of the
discovery of the error;
but made the required
recalculations and
adjustments within
180 days.

The Balancing
Authority did not
recalculate PIIhourly and
adjust PIIaccum within
180 days of the
discovery of the error.

Page 5 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
R#

Time
Horizon

VRF

Violation Severity Levels
Lower VSL

Moderate VSL

High VSL

Severe VSL

R3

Real-Time
Operations

Medium

The Balancing
Authority operated
during a calendar
quarter without ATEC
in service for more
than an accumulated
24 hours, but less than
or equal to 72 hours.

The Balancing
Authority operated
during a calendar
quarter without ATEC
in service for more
than an accumulated
72 hours, but less than
or equal to 120 hours.

The Balancing
Authority operated
during a calendar
quarter without ATEC
in service for more
than an accumulated
120 hours, but less
than or equal to 168
hours

The Balancing
Authority operated
during a calendar
quarter without ATEC
in service for more
than an accumulated
168 hours.

R4

Operations
Assessment

Medium

The Balancing
Authority did not
compute PIIhourly,
PIIaccum, and IATEC
within 50 minutes, but
made the required
calculations in less
than or equal to two
hours.

The Balancing
Authority did not
compute PIIhourly,
PIIaccum, and IATEC
within two hours, but
made the required
calculations in less
than or equal to four
hours.

The Balancing
Authority did not
compute PIIhourly,
PIIaccum, and IATEC
within four hours, but
made the required
calculations in less
than or equal to six
hours.

The Balancing
Authority did not
compute PIIhourly,
PIIaccum, and IATEC
within six hours.

R5

Real-Time
Operations

Medium

N/A

N/A

N/A

The Balancing
Authority is not able
to change its AGC
operating mode
between Flat
Frequency (for
blackout restoration;
Flat Tie Line (for loss
of frequency
Page 6 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction

R#

Time
Horizon

VRF

Violation Severity Levels
Lower VSL

Moderate VSL

High VSL

Severe VSL
telemetry); Tie Line
Bias; or Tie Line Bias
plus Time Error
control (used in ATEC
mode).

R6

Operations
Assessment

Medium

N/A

N/A

N/A

When making
adjustments to hourly
Inadvertent
Interchange or ∆TE,
the Balancing
Authority did not
recalculate the PIIhourly
and the PIIaccum for the
On-Peak and Off-Peak
periods.

R7

Operations
Assessment

Medium

N/A

N/A

N/A

When making any
month-end meter
reading adjustments
to Inadvertent
Interchange, the
Balancing Authority
did not make the
same adjustment to
the PIIaccum.

Page 7 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction

R#

R8

Time
Horizon

Operations
Assessment

VRF

Medium

Violation Severity Levels
Lower VSL

Moderate VSL

High VSL

N/A

N/A

N/A

Severe VSL
The Balancing
Authority paid back
Inadvertent
Interchange using
bilateral and unilateral
payback rather than
using ATEC.

Page 8 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
Guidelines and Technical Basis
Background
In February 2003, the WECC Automatic Time Error Correction (ATEC) Procedure (Procedure)
became effective for all Balancing Authorities in the Western Interconnection. The original
intent of the Procedure was to minimize the number of Manual Time Error Corrections in the
Western Interconnection. ATEC provides the added benefit of a superior approach over NERC
Reliability Standard BAL- 004-0 – Time Error Correction for assigning costs and providing for
the equitable payback of Inadvertent Interchange. In October 2006, the Procedure became a
WECC Criterion. In May 2009, FERC issued Order No.723 that approved Regional Reliability
Standard BAL-004-WECC-1 - Automatic Time Error Correction, as submitted by NERC. In
addition, the Commission directed WECC to develop several clarifying modifications to BAL004-WECC-1 using the FERC-approved Process for Developing and Approving WECC Standards.
The Effective Date of the BAL-004-WECC-1 standard was July 1, 2009. BAL- 004-WECC-1
required Balancing Authorities within the Western Interconnection to maintain
Interconnection frequency within a predefined frequency profile and to ensure that Time
Error Corrections were effectively conducted in a manner that did not adversely affect the
reliability of the Interconnection. In September 2009, WECC received WECC
Standards/Regional Criterion Request Form (Request) WECC-0068, which was a request for
modification of BAL-004-WECC-1. In July 2010, the chair of the WECC Operating Committee
assigned the Request to the Performance Work Group (PWG) for development.
Requirement R1:
Premise: Each Balancing Authority should ensure that the absolute value of its PIIaccum for both
the On- Peak period and the Off-Peak period each individually does not exceed 150% of the
previous year’s Peak Demand for load-serving Balancing Authorities and 150% of the previous
year’s peak generation for generation-only Balancing Authorities. The Balancing Authority is
required to keep each PIIaccum period within the limit. For example, the Balancing Authorities
actions may include:
•

•
•

Identifying and correcting the source of any metering or accounting error(s) and
recalculating the hourly Primary Inadvertent Interchange (PIIhourly) and the PIIaccum from
the time of the error;
Validating the implementation of ATEC; or
Setting Lmax equal to L10.until the PIIaccum is below the limit in Requirement R1.

Justification: PIIaccum may grow from month-end adjustments and metering errors, even with
the inclusion of IATEC in the ACE equation.
Goal: To limit the amount of PIIaccum that a Balancing Authority can have at the end of each
month.
Requirement R2:
Premise: When a Balancing Authority finds an error in the calculation of its PII, the Balancing
Authority needs time to correct the error and recalculate PII and PIIaccum.
Page 9 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
Justification: The drafting team selected 90 days as a reasonable amount of time to correct
an error and recalculate PII and PIIaccum, since recalculation of PII and PIIaccum is not a realtime operations reliability issue.
Goal: To promote the timely correction of errors in the calculation of PII and PIIaccum.
Requirement R3:
Premise: When a Balancing Authority is not participating in ATEC, payback of PIIaccum is
delayed.
Justification: The limit of 24 hours per quarter discourages a Balancing Authority from
withdrawing ATEC participation, for example, for economic gain during selected hours. If the
limits were increased to 60 hours, a Balancing Authority could technically withdraw ATEC
participation for one hour from Monday to Friday.
Goal: To promote fair and timely payback of PIIaccum balances.
Requirement R4:
Premise: PIIhourly, PIIaccum, and IATEC should be determined before the next scheduling hour
begins.
Justification: To promote timely calculations 50 minutes was selected because it is before the
next hour ramp begins and permits time to collect the data and resolve interchange metering
values.
Goal: To promote the timely calculation of PIIhourly, PIIaccum, and IATEC.
Requirement R5:
Premise: The ACE equation, and hence the AGC mode, will contain any number of parameters
based on system operating conditions. Various AGC modes are identified corresponding to
those operating conditions, as well as the specific sets of parameters included in the ACE
equation.
Justification: Changing to the proper operating mode, corresponding to current operating
conditions, affords proper movement of generating units in response to those conditions. The
addition of the ATEC term results in an additional AGC mode and a different set of parameters.
The inability to correctly calculate the ATEC term would dictate that AGC not be operated in
the ATEC mode.
Goal: To set the AGC mode and calculate ACE in a manner that corresponds to the system
operating conditions and to accommodate changes in those conditions.
Requirement R6:
Premise: Hourly adjustments to hourly Inadvertent Interchange (II) require a recalculation of
Page 10 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
the corresponding hourly PII value, the corresponding PIIaccum, and all subsequent PIIaccum for
every hour up to the current hour.
Justification: As PIIhourly is corrected, then PIIaccum should be recalculated.
Goal: To promote accurate, fair and timely payback of accumulated PII balances.
Requirement R7:
Premise: Month-end meter-reading adjustments are made, for example, when a Balancing
Authority performs monthly comparisons of recorded month-end Net Actual Interchange (NIA)
values derived from hourly Actual Interchange Telemetered Values against month-end Actual
Interchange Register Meter readings.
Justification: Month-end adjustments to IIaccum are applied as 100% PIIaccum. 100% was chosen
for simplicity to bilaterally assign PIIaccum to both Balancing Authorities, since the effect of this
metering error on system frequency is not easily determined over the course of a month.
Goal: To provide a mechanism by which corresponding month-end II adjustments can be
applied to PIIaccum, when such adjustments cannot be attributed to any one hour or series of
hours.
Requirement R8:
Premise: ATEC includes automatic unilateral payback of Primary Inadvertent Interchange and
Secondary Inadvertent Interchange.
Justification: Additional unilateral and bilateral exchanges disturb the balance and distribution
between Primary Inadvertent Interchange and Secondary Inadvertent Interchange throughout
the Interconnection; thereby stranding Secondary Inadvertent Interchange.
Goal: To not strand Secondary Inadvertent Interchange.

Page 11 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
Version History

Version
1
1
1

Date
February 4, 2003
October 17, 2006
February 6, 2007

1

February 6, 2007

1

February 6, 2007

1

February 6, 2007

1

June 19, 2007

2
2

December 19, 2012
October 16, 2013

Action
Effective Date.
Created Standard from Procedure.
Changed the Standard Version from 0 to
1 in the Version History Table.
The upper limit bounds to the amount of
Automatic Time Error Correction term
was inadvertently omitted during the
Standard Translation. The bound was
added to the requirement R1.4.
The statement “The Time Monitor may
declare offsets in 0.001-second
increments” was moved from TEoffset to
TDadj and offsets was corrected to
adjustments.
The reference to seconds was deleted
from the TE offset term.
The standard number BAL-STD-004-1
was changed to BAL-004-WECC-01 to be
consistent with the NERC Regional
Reliability Standard Numbering
Convention.
Adopted by NERC Board of Trustees.
A FERC Letter Order was issued on
October 16, 2013, approving BAL-004WECC-02. This standard will become
enforceable on April 1, 2014.

Change Tracking
New
Errata
Errata
Errata

Errata

Errata
Errata

Page 12 of 13

BAL-004-WECC-3 ─ Automatic Time Error Correction
Version
3

Date
December 6, 2017

Action
Approved by the WECC Board of
Directors.

3

February 8, 2018

Adopted by the NERC Board of
Trustees.

3

May 30, 2018

Change Tracking

Five-year review. The
project: 1) relocates the
Background section to
the preamble of the
Guidance section, 2)
adds On-Peak and OffPeak parameters in
Requirement R1/M1, 3)
addresses WECC
Interchange Tool
software successors
throughout, 4)
conforms the
document to current
drafting conventions
(R1/M1, R4/M4), and,
5) addresses nonsubstantive syntax and
template concerns.

FERC Order issued approving BAL-004WECC-3. Docket No. RD18-2-000

Page 13 of 13