Bal-004-wecc-002

WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction
A. Introduction

1. Title:

Automatic Time Error Correction

2. Number:

BAL-004-WECC-02

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).
6. 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 the current NERC Reliability Standard BAL004-0 – 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
BAL-004-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. BAL004-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.

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WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction
B. Requirements and Measures
R1. Following the conclusion of each month each Balancing Authority shall verify that the

absolute value of its Accumulated Primary Inadvertent Interchange (PIIaccum) for both
the monthly On-Peak period and the monthly Off-Peak period are each individually less
than or equal to:
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.
[Violation Risk Factor Medium:] [Time Horizon: Operations Assessment]
M1. Forms of acceptable evidence of compliance with Requirement R1include but are
not limited to any one of the following:
•

Data, screen shots from the WECC Interchange Tool (WIT),

•

Data, screen shots from the internal Balancing Authority tool, or

•

Production of data from any other databases, spreadsheets, displays.

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:
• Data, screen shots from the WIT,
• 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,

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WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction

•

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

R4. Each Balancing Authority shall compute the following by 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 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]
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 that demonstrate
compliance,
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WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction
•

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 that demonstrate
compliance,

•

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

•

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.
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.

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WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction
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

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WECC Standard BAL-004-WECC-02 ─ 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.

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WECC Standard BAL-004-WECC-02 ─ 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

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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

WECC Standard BAL-004-WECC-02 ─ 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.

R8

Operations
Assessment

Medium

N/A

N/A

N/A

The Balancing
Authority paid back
Inadvertent

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WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction
R#

Time
Horizon

VRF

Violation Severity Levels
Lower VSL

Moderate VSL

High VSL

Severe VSL
Interchange using
bilateral and unilateral
payback rather than
using ATEC.

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WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction

Guidelines and Technical Basis

During development of this standard, text boxes were embedded within the standard to explain the
rationale for various parts of the standard. Upon BOT approval, the text from the rationale text boxes
was moved to this section.
Requirement R1:
Premise: Each Balancing Authority should ensure that the absolute value of its PIIaccum for both the OnPeak 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 take action 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.
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 real-time 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.

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WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction
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 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.

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WECC Standard BAL-004-WECC-02 ─ Automatic Time Error Correction
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 particular 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.
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

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